He won't have, as of yet, as the 600s haven't started. I believe he's done at least a BRM 200k, but the 300k seems unlikely - he was injured around the time the 300s started and the intention, AIUI, was to ride an easier, flatter SR series. If ACP aren't willing to allow some accommodation, then he might be forced to ride 3x600k. Normally that would be a cake walk for Steve (and indeed I'm intending to do this myself, though it won't be a cake walk) but given his injury, it could be tricky.
I'm sure if Steve and his team are looking at PBP, they will be thinking about this very carefully. Steve might well be forced to ditch PBP in order to keep the record attempt on track, but hopefully that won't be necessary.