I personally have never noticed flaws when such tecniques are employed, but it may be just immersion doing its job. I’ve never heard of Austin Power being singled out for its special effects…

Compositing has been a thing for, like, forever, going from cutting and gluing film together to, well, having lookalike instead of the real actor in certain shots…

I’m mostly weirded by how you found out only now. I guess go and have fun looking up “Captain Disillusion” youtube channel.