It does somehow work but it affects a wideband of frequencies rather than a single specific band namely the 5.5khz part, and only a few dbs at best. If you’re fine with that, there’s no harm in trying. Here's someone else's finding for reference.
I did give it a try on my ex600, and it didn’t work as well as I’d hope, but again ymmv. On the other hand, I also experimented with different bore sizes, foam tip vs silicone tip, trying different cables. The things we're willing to do hahaha. But on the upside, while many will be up in arms on this, the simplest solution sometimes is the one often overlooked: EQ. Give it a shot. Here’s a screenshot of mine.
Solves the bass and hot treble issue, plays well on all of my songs, gives it a playful tuning while still being detailed and not losing on instrument separation. Best case of course is using a parametric eq, but not everyone has easy access to that. I’m already hearing angry chants of “why would you ruin it with a v shaped tuning” but it’s all subjective anyway and there’s nothing wrong in trying to make it sound exactly as you want it to be, even if it goes against conventional wisdom.