You're right -- this is a mitigation that highly ethical/moral companies will take. It's likely that EULAs/ToS permit experimentation at any time on any version of an application though.

There's also the question of how much of a lab rat people really consent to being -- given that you can't really know what experiments will be run ahead of time.

What are the disclosure rules? What is an experiment versus what is not? What is legal to use to experiment on people with? This is the kind of place regulation is normally present, and it hasn't caught up yet.