Because it is more dangerous to underestimate your enemy than it is to overestimate them.
Also, I like how you’re moving the goalposts here. You initially said they couldn’t recover aircraft. Clearly they are recovering aircraft. Now you’re claiming that you’d said they were capable of sustained flight ops, which was not at all mentioned in the original post.
they can’t recover aircraft. not in any way that goes beyond the abject meaninglessness of a youtube video — which may be the very height of meaninglessness.
but certainly not in the way that anyone would bother to build aircraft carriers in the first place — which is to perform sustained flight ops, potentially under combat conditions.