He means video draw poker machines, where you get paid a multiple of your bet depending on your final hand. Most online casinos used to have bonuses where the required wagering amount to clear the bonus multiplied by the return value of certain games led to a positive expected value for the player. So as example you'd deposit say $100, get $100 bonus, wager on video poker for $2000, getting back 99% of the wager for average of $20 loss from the wagering and $180 cashout. Much more rarely there also were some games that when played optimally, would give slightly over 100% return for your bet. The casinos were banking on most players playing them suboptimally and/or getting hooked.

Even though it's +EV for the player, you'd need some bankroll to ride out the variance as you could lose on X casinos in a row. Ages ago these were really +EV and you could usually just autoplay them with small bets, so the bankroll requirements weren't that harsh. Later on the wagering requirement on the bonuses grew, often making the small bet grind unprofitable, but you could still find profitable situations when played with correct bet sizing. But those needed much bigger bankroll as usually it was more +EV the bigger the bets you made, so you'd often play many casinos for just a few minutes with big bets losing your deposit and bonus, but sometimes winning big and covering the losses with profit left over.