I feel the same for people who require very bursty working hours. Part of the job -- perhaps the most important part! -- is to collaborate with your team. If you want to spend 90m during the workday to go to the gym, make sure you're not holding your teammates back. We currently have two employees that do that and it works well for everyone. If you require 3 hour breaks mid afternoon, you're probably not going to work here.
And, everyone I've described manages to collaborate enough during the workday (and asynchronously at other times) despite often taking multiple hours per day for things like gym or family. I'm happy that I can hire such people, and I wish you luck in evolving your company to the point where you can similarly access the full pool of qualified candidates.
I think we've continued this conversation thread as much as we usefully can; thanks for an interesting exchange!
There are better ways to protect the employee, though: the legalese can omit time of day / day of week / place of work / equipment used as conditions of IP assignment. My current employer does this. (No it's not based in the US, but it is a startup funded by both US and home-country VCs).
Of course, the employer does own stuff created within the course of employment. Not a problem in any of the plausible future successful or failed exit scenarios.
Last thought: many good people in tech, very much able to do the jobs you ask of them, have ADHD, or kids, or athletic hobbies, or other reasons to do a bursty workday. Sometimes people seemingly outside these categories may turn out to be in them (e.g. new parents). Being incompatible with such workers makes it harder to hire and keep the talent tech companies need to succeed. (Sometimes it's illegal too, but that's a separate conversation.)