Agreed, I’m not saying it’s impossible to detect the OS, but it’s even more trivial for an adversary to regex the User Agent and serve the malware for that OS. The average user doesn’t even know what a User Agent is, and that’s who the drive by malware websites are counting on to infect because they’re easy targets.
Just like a real fingerprint, that will only identify the fingerprint to a person, not tell you that the fingerprint is from someone who is European. Fingerprints are used to track you across different websites, and build a profile of you for advertising.
Maybe this is launcher specific, but on Pixel phones, when pulling up the list of apps to switch to, there’s a screenshot button, which is way easier and can be done with one hand.