Yes, this could be the case. Or maybe some vats contain the outside-of-the-vat-world analogue of LSD or other psychotropic substances. Which leads me to the following questions:

If I am indeed a brain in a vat, how far can I trust my own thought processes (like a logical argumentation)?

And taking this further, could it be that I am only a part of a brain in a vat where the other part has already been replaced by computer controlled cyborg implants changing the way information is processed?

The impression that an argument is logically correct and plausible may be a phantom signal resulting from input into a specialized area in my remaining brain.

Even the thought that I had a thought is then maybe wrong. How would it feel to have the convincing impression that I am having very deep thoughts right now without ever been able to perceive one single aspect of these thoughts?