This is true. Maple is bright, but it has a very smooth top end.
My basses have cherry bodies (similar to maple in weight), with a purpleheart lamination between the back and top. My main bass has a birdseye maple top. The set necks are maple and purpleheart, with a phenolic (ebonol) fingerboard, and graphite.
So we have all the ingredients here for a bright bass, but it's actually very smooth sounding, not like a maple bolt on, which would have that bright attack.
The issue with EMG's is they have their own sound, and that's not the sound of the bass. It works well with some basses, and not with others. Since they have a kind of EQ'd tone, they might make some basses sound harsh.
On my fretless, the single DC in the MM "sweet spot" sounded great, but the same pickup in the typical Jazz Bass bridge position on my other basses sounded harsh and brittle.
New pickups can make a big difference!