The stress level and difficulty of teaching (while accurate statements) are not relevant to this issue. You can't excuse poor treatment of the biological needs of students simply because you have a very difficult job.
My comment was also not a reductive statement when I've been told "no" when I ask to go to the bathroom, or told "3 people have already gone to the bathroom, you'll have to wait until next period."
Both of these specific situations, and variations, happened to me. I watched a classmate pee their pants once when they were denied access to the bathroom.
Want to talk about job stress? Think about the stress an 8 year old goes through when every time they feel their bladder getting full they start worrying about whether they'll be allowed to pee, or have to wait until the next class or recess/lunch, learning nothing in the meantime and hoping they're not the next kid that has to have their parents bring a change of clothes.
I don't know what country you're in. I'm in the US, and quality of pay varies greatly from state to state. Workload (class size) often varies with the socioeconomic status of the people in that school district. What doesn't vary in any conversation I've had with people on this topic is that my experiences are very much not unique.