To be fair some people have naturally different "peak hours" and sleep schedules. I naturally fall asleep around 1-2AM and wake up at 10. Going to bed earlier involves tossing and turning for hours annoying the SO. Staying up for 36 hours to "reset" works for a couple nights before the schedule drifts back to its natural state.

I practice sleep hygiene and have tried cutting out caffeine. Conversely, there's no amount of caffeine capable of facilitating deep work before 10:30-11AM, just end up frantically clicking around articles and wishing for sleep.

Maybe these people aren't trying to game the optics, they just are naturally at their most productive from 11-7. IMHO it's awesome that your company allows that kind of flexibility (and that the morning startup is at 10:30!)