>>Every single free app adopts a very similar business model.

There is NO guarantee that non-free apps don't do the same.

That said, I'm the same as you: I use 'free' version as a short-term trial, uninstall in short order, grab the paid one if I liked the 'trial' version - in the HOPES that they won't do that - but I'm very aware that I'm doing this on trust.