Eh, I didn't know ePBT were willing to reverse dyesub a whole set. That insane amount of QC it would take is probably not worth it for them.
Did they confirm to you that they'll do it?
Haven't they done a black on grey kit before?
Then again they seem to be really inconsistent on what they can and can't do as of late.
Black on grey can be dyesubbed normally, as it's not a lighter legend on dark background. This is Light legends on dark background, it can't be dyesubbed normally - which means it'd have to be done some other way, like reverse dyesub/allover-dyesub.
To my knowledge, ePBT have never done it, and probably for the reason that it's too much to do currently. They do reverse dyesub accent keys because it's a lot less work (I think for epbt kuro/shiro, or did they outsource?). If they leveled up and are willing to reverse dyesub whole sets now, then that would be awesome and opens up a lot of possibilities!