Is there any direct support in the film for that view?
If the writing doesn't support it, then that's kind of like asking if Speed is set in the Matrix: unfalsifiable and not useful.
Yes, there are plenty. Now we can debate perception all day, but I think this sampling is enough to pique interest..from what I can remember:
we don't know caleb's history
he has a big, unexplained scar on his back
there is a lot of focus / talk about iterations of the AI
caleb is the one locked in an observation room when he has talks with ava
the cutting himself scene is...odd and unnatural
he never, ever gets drunk
there's a weird scene towards the end where nathan refuses a drink from caleb and goes out his way to make him take a sip and asks how it tastes (he does not answer)
the conversations btw nathan and caleb are not exactly natural, in that nathan consistently prods caleb to provide more in depth/opinionated answers and not be so technical
added: wouldn't the best test of an AI be to give the AI freedom and see if it recognizes itself as AI?
Not really, as "recognizes itself as AI" presupposes a difference between AI and human. Gimmicks aside (i.e. let's see what's inside me), any AI which recognizes itself as AI would essentially fail the Turing test.
To me, those bits just came off as Lost/Shyamalan-esque hand waiving without saying something definite. Anyone can write a profound question they don't intend to answer.
The spinning top in Inception, or the dream in Blade Runner, are far more intentional.