I dont think higher profit will decrease our bonus but higher loss will increase our bonus. It wont make any sense if higher profit decrease the bonus, as someone may get nothing if it is implemented to the calculation of the bonus. I'm guessing there is still at least a minimum bonus amount for each rank (will be decreased if there is no activity) and additional amount will be based on wagering stats + losing stats only. Profit wont affect the bonus because if players are in profit then Stake will use rank + wagering stats only imo. I'm not sure about house edge, afaik it does affect on the rakeback only but I might be wrong.
Exact method of bonus calculation is unknown and we have no clear idea on what makes it higher or lower, sure it makes sense to say that losing more should mean a lot more bonus, that is understandable because that makes sense even if you do not know, but there is no guarantee about it, higher profit shouldn't increase or decrease our bonus but based on wagering maybe you could have more.
So some guy who wagered 100k and lost 10k could get less bonus than some guy who wagered a million dollars but made 50k profit, because there is 10x higher wagering there, and that could be a good reason as well, the more you wager the more you profit. So in the end, we are talking about a good amount of profit here no matter what, and that could be a good reason why profiting doesn't prevent you from making more.