You are correct whenever I have a layout like this, I will make the bathroom 5'6"-6' Wide, Steal a few inches from the adjacent rooms. But your question was about a window over a tub, Yes you can do it but I prefer not to, I was just offering an alternative.
I work from home and often I will get fixated on solving a problem a certain way, sometimes I need to step away from a project for awhile or I need a little push from an outside source to help me rethink my approach.
Cheers