>Is Meta actually obligated to repay the loans or not?

They aren't, but they're obligated to pay leases for it (they can't just build the datacenter and then walk away), which is kind of like having to repay the "loans".

I'm not an accountant, but "contractually obligated to pay" sounds like a debt to me.

If the Generally Accepted Accounting Principles don't require that to manifest on the balance sheet, then it sounds like the principles aren't very good ones.