this whole forum is pretty much dedicated to this.
I don’t know about the other sections in this forum but I have the impression that many threads in the road section are about vendors that have more or less established their own brand identity with frames that are similar to main stream frames.
With those brands you have a higher chance of getting spares down the road.
Getting replacement parts like fork is probably always hard if the vendor vanishes or doesn’t offer that part anymore but you can still use other stems/handlebar combos. And I think that is the main disadvantage.
I often read posts about the flexibility of chinese carbon handlebars, so if you’re not satisfied with the one supplied what are you gonna do? Buy one from cervelo for 400? (Just a guess)
So no, intuitively i don’t think it’s the same.