I’d say the opposite. Having fitted a load of Resound and historically Bernafon I’d contest that the Resounds have more Low/Mid range punch - especially with a closed dome and the bigger receivers. In any case, you’d be able to modify the response.
The main issue here is going to be venting - if you can put up with a fully occluded mould, it will sound better almost irrespective of what’s driving the higher pitches.