I think employers thought “hybrid” was good way to get employees to agree to going back to office. In reality, I think it was good way for employees to get employers to agree to effectively fully remote work without explicitly demanding it.
It’s like in Office Space:
PETER I, uh, I don't like [the office]. I don't think I'm gonna go anymore.
JOANNA You're just not gonna go?
PETER Yeah.
JOANNA Won't you get fired?
PETER I don't know. But I really don't like it so I'm not gonna go.
JOANNA LAUGHS) SO YOU'RE GONNA [go fully remote]?
PETER No, no, not really. I'm just gonna stop going.
The net effect is: stuff is getting done anyway and people that like going to the office have a better time because it's not crowded.
We (my team and me) sometimes decide to meet at the office but don't have to wander around looking for an empty meeting room.
So to sum up: yes, rules are arbitrarily made up.