Thank you. I was reprimanded once for essentially "only" being at the office for the defined time we agreed I would be there. I spent some time racking my brain until I decided I wasn't being unreasonable.
There is this hyaundai commercial ( https://www.youtube.com/watch?v=UZ8Klm8vPlI ) that hits home for me. "When did leaving work on time become an act of courage". It's so true.
I've always found it humorous that the clock hits 6:00 rather than 5:00. "Leaving work on time is an act of courage, but let's not get crazy!" Presumably he courageously started at 10:00 or took an hour away from work for lunch.
It's more about the appearance of working vs actually having work to do. I used to come in at 7:30 and leave at 4:30 because my commute was terrible other wise (2 hours each way). The few nights I stayed until 6-7pm I noticed the engineers that came in at 10-11am were all gone by 5:30pm but to most managers it looked like they were "working harder" than me when I left at 4:30.
Unreasonable employers happen. You have a variety of options including try to convince them to be reasonable, accede to their demands, try to be sneakier, or find a new job.
In our industry where it tends to be an option for us, "find a new job" might make sense.