I get this and people have tried to assuage me throughout my career with things like "yeah but it's up to the manager so you'll be fine" or similar. I absolutely hate manager-discretion "perks" because they aren't official ("on the books"), they can be taken away at a moments notice on the whim on your manager or if a new manager comes in who doesn't agree.

Before COVID this was the case with WFH at my last company. I was able to WFH for 2 days a week but it was impossible to get that codified in the handbook. I was even on the committee that oversaw edits/rewrites of the handbook but HR would not let us add anything about WFH other than "It's up to the manager". I had so many people tell me "I don't know why you are so bothered, you are able to WFH". Yes, today, right now, with this manager, or at least this managers current demeanor I have WFH but all that can turn on a dime, I wanted it to be official. "Of course", the company as a whole couldn't allow WFH, that would be "impossible". I left that company in late 2019 and... surprise! They went fully remote in 2020 and now are a hybrid with the majority of people WFH-ing. It was a rare case of being told it was impossible and would never work to seeing not but a few months later all their arguments to be shown for the BS they really were.