Are two address belongs to same wallet ? If not we can't call them alt account just because of transaction from gambling wallets. Same like also for exchange wallet, if you and me use same DeX for sell token it doesn't mean we are alt. If address created for same wallet and use it on same signature then we can assume that they are alt. I think we need more careful about detect alt account, we shouldn't tag someone by suspicion only (IMO). Transaction made on each other also not strong proof of alt account. We can exchange something each others, so it would not consider alt account also.