I think the reason people want it to beat forretress and skarmory is because they aren't *just* walls, but they're secondary users. "wall" doesn't have much relevance to his case.
If CAP 9 has things that it cant beat, i.e Gliscor, Skarmory, Hippowdon, I think that we should be aware that attacking moves aren't the only solution to these pokemon. Rapid Spin is an example of stopping entry hazards; moves like taunt prevent these pokemon from setting up. I'm aware that admiral korski brought this up earlier, and I think it's a point that needs to be addressed further. I'm not saying that this method is obviously better than the mixed option, but mixed would make us lose out on some power we might need for the the sheer power of the pokemon itself, and not just to beat pokemon x y and z, which can be handled in another way.
Going Physical doesn't necessarily force a terribly low special attacking stat, and there are definitely ways to counteract this. Metagross, for example, is a pokemon that is Physically biased, yet has a 95 base Special Attack. Yeah, I know that Metagross has a 600 BST, but even if you take 10 base points from defense and special attack, and take off 20 from attack, you get 115/110/85 respectively, which still falls under physical.
SE moves can still do a number on some physical threats to this CAP; and it's not like this CAP is totally helpless against said pokemon. Who says it won't get something that helps against entry hazards? Hell, Skarm/Hippow/Gliscor probably won't be able to touch CAP 9 as much as CAP 9 can touch them.