I know several people who do this………Spuds, Arsenal, Chelsea fans at least. Not all STHs at their ‘big’ clubs, but like to watch the occasional PL game (as a neutral) and obviously use it when ‘their‘ team is at the Amex.The strange thing with all of this is that we have a number of 'members' who pay the £30 membership fee who are actually fans from other clubs, mostly in London. I knew of four fans when I was working who were Chelsea, Tottenham, and Palace fans but also paid for memberships to us, so they could buy tickets at the Amex in the home end, and generally kept their allegiances quiet at these games, in order to be able to get to see their teams play away.
For them the £30 membership fees didn't put them off even if they only bought a ticket once a season when their team visited the Amex.
To me this is worse than the issue of the OP on this thread. The club must know that this goes on but if you are a 'paid up member' there's little they can do, unless they misbehave in the home stands.