The implication I read was that the if the surrounding area was full of standees. As for the question, I would guess that unless you have a way with words to persuade the standees to move, and the guard is on your side, you're ****ed
It says
if the bike storage area is rammed - not the area around the bike storage area. I'd just ask people to move.
All this is hypothetical anyway, as usual relying on the doom-laden scenarios that seem to be favoured by so many here.
There will be lots of extra seats provided overall, so maybe lots of people won't be standing in the first place. I'd venture to suggest that it's rather less likely to be an issue on a GWR IEP than getting at the bike spaces on an XC Voyager can be...
Never mind that there will be more trains running, so that if we return to the Reading-Cornwall angle, there will be 2tph most of the day at least as far as Exeter, and the nine-car sets will have 10 bike spaces - there are four in a five-car set - so there will be a fair few extra bike spaces available, on top of the extra seats.