I think it is a bit of a stretch to blame it on President Obama. Personally, I think that the true cause of the lack of pictures is stricter enforcement of rules already in place since... I don't even know when. Part of it can be attributed to a desire for greater secrecy, but part of it is certainly the result of hiring competent people for security jobs.
It's far more of a stretch to suggest that the PLA, PAP, Ministry of Internal security and many other nameless Chinese security agencies didn't have competent people working security until a few weeks ago.
The rules were always in place. Just think back to how long they managed to keep almost all pictures of the J10 under wraps until they were good and ready to unveil it.
Chinese military policy towards secrecy could be pretty accurately summed up by the old Chinese proverb, which roughly translates as, 'the strong flaunt their strength, while the weak flaunt their weakness'.
When you are powerful to the extent that your opponent cannot hope to match you, then you want to remind your opponent of that at every opportunity to cow them into backing down when your interests clash, and/or into pouring way too much money into their military and bankrupting themselves to win without having to fight USSR style.
When you are weaker, you want to hide your capabilities so you can use the element of surprise to help overcome any technological and/or numerical disadvantages.
In practical terms, PLA acquiesce towards military enthusiasts started after the military balance started to shift overwhelmingly towards China's favour across the Taiwan Strait, and also as tensions between the Taiwan Straits eased.
During that time of minimal risk of military conflict, there is much PR/propaganda value to be had in flaunting your military might to both boost domestic moral/pride, and also to cow potential adversaries/foes.
The other consideration would be to stoke American paranoia and ego so they end up vastly overspending on the military to the detriment of the economy.
Think the unusually open nature of many prominent programmes from ASAT to AShBM to hypersonic gliders to the J20 and any number of other major revelations 'leaked' in recent years. Each and every such announcement and leak was met with much consternation and concern from the US, prompting military and political leaders to demand vast sums to develop counters to those new Chinse developments.
But that strategy only makes sense when there is minimal chance of an actual armed conflict actually breaking out.
When tensions rise to the point where the possibility of armed conflict could not be dismissed out of hand any more, more short term considerations must now take sway.
After all, it would be a major own goal to goad the US into vastly overspending on arms playing the long game if you actually end up getting into a fight with them in the short to medium term, where those arms would actually come in extremely handy, while China was banking on another few decades of peace, by which time all those weapons bought with those extra billions and trillions would become obsolete and irrelevant.
The biggest immediate changes to make China re-evaluate it's risks assessment would be rising tensions in the SCS, orchestrated by Harris but ultimately green lighted by Obama. Their recent words and deeds cannot be ignored or dismissed, and Chinese military posturing and strategy would need to be adjusted accordingly.
I also think there is also a degree of hedging going on in preparation for either Hillary or Trump.
Hillary would be like Obama on cocaine as far as her likely China policy is concerned. If you think tensions are high now, just wait till Hillary gets her mitts on the big red button.
Similarly, Trump is a very big wildcard who could do just about anything. While most neutrals desperately hopes his rants are all just a carefully crafted and maintained guise, I would say the odds are just as good that he actually believes the crazy he is saying and will try to actually do some of the more outlandish things he has been promising.
I would actually say that the chances of a real all out shooting war in the SCS (and pretty much globally) would be considerably higher if Trump wins precisely because he is so unpredictable.
Hillary hates China with a zeal, but at least her actions and choices would be largely governed by logic and reason, and so predictable.
With Trump, there's a good chance he might give orders that start a war by accident or through sheer stubbornness or even if he is just grumpy cos he couldn't get his fake hair just right.
No matter how you cut it, the risks of armed conflict between China and the US is likely to rise irrespective of which of the two front runners ultimately wins, and so now China is adjusting its long game from one of goading the US into unsustainable military spending, into its more traditional denial of all information mode to make it much harder for the US to be able to focus its defense spending and developments to target specific Chinese breakthroughs and developments.
