Guild is some exception, not so common in unions. Always it end up more like typical aflcio union. I also have made some switch between front end and back end in job, have done some security job and back to normal developing, all these are usually harder in unions. Maybe in theory it is not required but in practice it is almost always this way.

Also I have started prior tech company, it would have been hugely difficult if i had to make negotiations with unions.