This is a technicality, users do not care about technicalities, they have their own expectations and if you are on -say- a stable branch with autoupdates enable

This is a technicality, users do not care about technicalities, they have their own expectations and if you are on -say- a stable branch with autoupdates enabled your expectation is that you'll get the latest version that everyone else is using. A/B testing through that branch breaks that expectation (and no, mentioning it somewhere hidden in some EULA or equally obfuscated place does not mean people will not have the expectation - hell, even mentioning it right below the download wont make a difference).