The DF-17s in parade are likely mock-ups, as real missiles are all sealed in that well maintained can environment to extend their life span(if you watch that DF-26 launching video you'll notice that its very different from the ones on parade. ), so all we get from these pictures is its shape, likely nothing else.
Does China need to make so many mock-ups? How difficult to re-seal the 16 DF-17 missiles into their storage can after the parade? How much life span could be lost after a few hours exposure in Tienanmen Square, and during the whole period of parade preparation?
From the angle they are positioned on the TEL during the parade, it is clear that the PLA wants people to have a very good view on the smooth and flat belly of the glider vehicle. Why did the PLA do this? Is it intended to assure that people can correctly identify they indeed are gliders?
If the purpose is to send out an unambiguous message to American hawks, wouldn't using mock-ups compromise all the efforts?
To me, unveiling DF-17 at this particular juncture is equivalent to firing a warning shot, kind like a silent version of "Don't say I didn't warn you before anymore!" It is possible that China wants to use this opportunity to warn US hawks not to risk US naval warships to do something stupid within the striking range of DF-17, i.e., in the South China Sea and in the Taiwan Strait, because China may have sensed Trump will gamble something really big to boost his chance of re-election, given the facts that Trump's trade war can go nowhere, his Iranian sanction sucks, and a recession is on the horizon.
Trump has very strong narcissistic tendency. All of his misfortunes during his time in the White House can be traced down to his personality, overestimating his own cards, and underestimating his opponents' cards. If his yield to N. Korea, after Little Rocket Man insulted him with an H-bomb explosion and numerous missile firings, was because of his worry of China's intervention and of the vulnerability of the Eighth Army stationed in S. Korea, and if his yield to Iran, after the Turban Man insulted his by shooting down his expensive spy drone, was because of his worry of the vulnerability of US military bases in the Gulf countries, he may naively believe the US navy is immunized from enemy's attacks, thus may inadvertently use US naval warships to gamble something big. In this case scenario, the storage life span of these 16 DF-17s probably is the last thing China is concerned.
Trump has to gamble within one year and these DF-16s may have to be used for combat missions within one year, why bother to put too much emphasis on their storage life span? This seems unreasonable.
