Typically these are candidates, most of whom are already working right? So their visa would be tied to their current employer and they are not allowed to work f

Typically these are candidates, most of whom are already working right? So their visa would be tied to their current employer and they are not allowed to work for someone else. 5-10 hours would be similar to a typical interview loop yes, and if that was the entirety of it then it's not more time consuming than the typical engineering interview.