I have 1 book that does it that way. But their bonuses are smaller.
The rest have separate accounts. One for your deposited money which is the regular account and a second account for the free play balance. so when you bet $100 from the free play account, the wager will say free play wager and if you win only the winnings go into the regular account.
Dietz can you explain this to your fellow troll, who doesn't believe me, but has no idea what he doesn't believe.
A 200% bonus is really worth 100% of your actual bonus. By doing it this way they can claim to be offering a bigger bonus. but that bigger bonus is only worth 5-% of what it says. Just like a Matchplay chip (one time use) is only worth 50% of face value. (47% actually) (different amounts for different games I guess.