You are mostly right as we can see in recent conflicts. But we also need to realise that fact all the recent conflicts do not 100% represent any future conflicts China might face, either.
So, while China has the time and money to invest in heavy attack helicopters (or any other hardware/technologies) now, it's better to get it done now. Definitely not waiting to find out it's lacking certain military hardware or technologies while an armed conflict is ongoing. Then it will be too late...
It's a bit like school education really. We learn a wide range of subjects to prepare ourselves for the future as long as we can afford to do so. And China right now can afford to do so.