Front office and back office is the classic financial services split: front office generates revenue (trading, sales, deal teams), back office runs settlement, operations and support, with risk and compliance often called middle office.
The split shapes hybrid policy more than any org chart: front office roles tend to carry stricter attendance expectations and fixed positions, while back and middle office flexed first and hardest. One building, two or three different workplace models, which is exactly the scenario zone-level booking rules exist for.