Yes, +EV if we're being technical but I'm only a layman so I like to keep it simple! The case I raised on the Yesbets group related to gambling one's own money on a slot without any bonus offer etc, therefore it was -EV. The user in question justified her accounting by saying it was the house's money, so it was therefore fine, and that she also had a "system", which it transpired is basically the Martingale strategy applied to slots.
I just think it's a very easy line to cross: matched betting into punting the odd "win" here or there. It's not what matched betting is about and I just don't think it has a place in a matched betting group. What concerns me is that someone (not sure who) actually punted their matched betting winnings on the slots, lost it all, and subsequently self-exiled himself from matched betting lest he generate a net loss. Despite someone mentioning the user who lost out, there was actually a new post soon after where someone was eagerly testing this new-fangled Martingale strategy on another slot! Surprise surprise, they came out with a loss.
Incidentally, I also think sports trading is another thing that gets conflated with matched betting too often, but that is a whole different kettle of fish entirely
Worth remembering that for every Peter Webb, there's a hundred (random number plucked out of the air) wannabe traders who bust out their bank without advertising it. Peter Webb, in particular, has a trading program to sell (he made Bet Angel), so of course his videos are going to make sports trading look effortless.