As a teacher, I have to say, the boundaries are clear. At least more clear than what these guys are saying. Sometimes there are some gray areas, but they're nothing like what these guys are doing. Yes, they get messy sometimes. I had to text some students of mine during the pandemic when they couldn't access their email attachments due to technical issues and zoom wasn't working. That felt like a line crossing, thought it was only assignments and stuff like "class is starting now, where are you?"

But in general texting my students? No way.

Teachers, at least me and my collegues, we are aware of our boundaries with students and we respect and honor them. You can't have trust with a teacher, and then have that teacher come onto you, or respond to an advance.

When I was younger I had many students come onto me. Of course this was when I worked with adults. Even then it didn't feel appropriate. If I really like someone, I would have waited until they were done taking my class before accepting a come on, and that was with adults. Teenagers? No way, not at all, not ever, not even after they turned 18. That's creepy.