It's relatively normal in countries that still have conscription, if you don't serve and don't get an exception, you go to jail, otherwise what is the point of conscription vs just making it voluntary. The more damaging thing for these teens will be the social and career repercussions they face for refusing to serve, they will be barred from many lucrative jobs that will automatically filter out people who refused to serve, etc.

Jokes aside, one of the kids said during the interview he was actually called an antisemite by classmates before. So there is that...

Still less likely to get killed I imagine.

I can't recall any stories of any objectors enduring anything particularly bad, maybe it would get worse if more people started doing it, barely anyone rejects their service, even during active moments of conflict