On moderately steep slopes like the Ben More route there isn't really a safety concern that an ice axe would address. The relevant consideration is comfort, which poles address better than an ice axe would
I've been involved in quite a few wee clambers up and down some super steep stuff on training exercises that poles are utterly useless on, in fact are more of a hindrance (for balance, I'm defo a pole user in normal circumstances!)
I'm not for a minute saying I'd take an axe in such circumstances, but I wouldn't say it'd be the wrong thing to do either.