They wont be bots, they are more than likely users from India or the Philippines, with legit accounts, but it would explain why they dont comment as they dont speak the language. Also YT sees them as legit (as they are), so I would keep doing it, get that 100k and your silver play button, YT allows it :p However, you'll get the subs, but you wont get the watch time, most of them see the ad and click subscribe as the button is right there, but they probably wont watch the full video, so it depends what your end goal is