If you already have an iPhone and you're on the phone a lot, or stream media from the phone a lot, then MFI can be very handy. But if you've been using a nice pair of headphones for media streaming, beware that the HAs simply cannot match and deliver the kind of sound quality a nice set of headphones can, especially in the low range if you like nice deep bass (and seems like you still have fairly normal hearing on the low ends so I'm sure that's important to you).
So if you want to still use quality headphones for media streaming even after you start wearing HAs, then that cuts down on the value of MFI a bit.
If you're not on the phone that much (like constantly for work/business), then that cuts down on the value of MFI a bit more. For your level of mostly just high frequency loss, I don't think you'd have too much trouble hearing on the phone even without HAs in the first place.
If you have an Android phone and would have to switch over to an iPhone to take advantage of MFI, then that makes MFI even less alluring.
Having said all that, I still dumped my Samsung Note 4 and bought an iPhone just so I can get MFI, even though I'm not on the phone a lot (except for business calls which I use a soft phone on my laptop), nor do I stream media from my phone a lot. So go figure. I didn't pick my current OPN HAs for MFI, but because it has MFI, I want that MFI nice-to-have convenience, just to have.:-)
HA wearer since the 1990's > Rexton Insite+ CIC (2011-2016) > Oticon OPN RITE (2016)
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