To bad, Stake can't make a test promotion for people who are not playing Sport. Maybe just a bonus balance only can be used on Sport, for non sportbet use to test the temptation ~XD.
Sports betting addiction and casino betting addiction works differently. They won't be able to turn a casino bettor into sports bettor by offering free bets. I haven't received any bonuses yet for sports betting activity as I rarely make bets on sports event at Stake.
BTW, have you tried to join the poker free roll tournament after completing the level 2 verification?