I don’t know. The algorithm used is a red-black tree and doing a delete ens up being 0-2 deletes and 1 insert if I’ve counted correctly. From what I know there is nothing special you can do with red-black trees to speed up deletion as you have to re-balance in any case. If we could know that there are multiple adjacent blocks being deleted at once we could join them ahead of time, but I think that would be very hard to know.
Maybe @sverker has some idea about if anything can be done?