Lol you’re right, it’s not a very precise method. Every colleague would judge slightly differently.
In my case I would say anyone older than me, and I’m in the middle! I’m so glad I don’t have to make that judgement anymore though as I felt for anyone in that situation and you are so right about lack of public restrooms - many cafes around here say their toilets (public not employee like ours) are for customers only I guess there just isn’t the drive to fund public ones.