I'm not an expert on IR or BBC, but I think big fat cocks are often not as rock hard as regular cocks. I have seen quite a few scenes with monster size cocks being a bit bendy. Perhaps it's a good thing, for the ladies who have to receive them.
The point is when you are that long and thick, it would do a great job of stuffing holes even if a bit soft. The exception being, as seen there, a closed anus. yikes. I'm really curious what happens in the end (pun!), how (if?) he wiggle that great worm into that tight hole. IMHO it's always the best seconds (sometimes stretching to one whole minute) of an anal scene, gaining the first entry.
(aside: why is there mosaic on the cover but it seems to be an uncensored vid?)