Well, it's like Boeing having investment from Canadian government, that does not make it a Canadian company lol. So does Airbus after Airbus acquired Bombardier...
Well, they will most definitely use C919 as a testbed for Chinese Tech on subsequent Chinese Aviation.
The problem is, unlike Military Aviation, there are quite a few different factors other than the ability to make engine or avionics that counts. Most Civ Air look for parts commonality, easy to maintain and cheap per flight hours, that is going to take a while to master and then a longer while to be able to make it as completable as western tech (Say what you want with Boeing Max, they are cheap to fly, which mean a lot of airlines are going to overlook the safety issue and buy them) on the other hand, Chinese Airline and its parts don't have any reputation, which mean they can't really bounce back if there are any accident occurred. I mean right now, if C919 gets into any kind of accident and suffer hull loss or even life loss, Chinese can blame it on western parts because it is using western part. But if they started to change to domestic parts and it got problem, that will kill the entire Chinese aviation industry before it can start, which mean China are going to take times to take that risk.