Technically, DHF HBD is already created but it is not included in haircut calculation. For the purpose of haircut, DHF paying out a proposal is adding new HBD in the pool.
I am not sure what the haircut consequences are (probably just devs taking the loss as they are paid less in USD value and the HBD pool still mildly inflating).
Yeah that sounds logical I guess, there's a lot involved with this but starting to understand it more step by step