Created attachment 289095 [details] patch to ebuild grub2-install can use efibootmgr to automatically configure the EFI Boot Manager for you. Patch attached for ebuild, don't know if this is the right way to do it but it works for me. Can efi-32 use efibootmgr too?
Created attachment 289097 [details, diff] patch to ebuild
You can use EFI without efibootmgr perfectly fine, so I don't see why this is needed. I have it set up on my new laptop (Thinkpad X220).
Another reason against it would be that even if you did use it once, you could then unemerge it because as long as you didn't change any configuration new grub2-install generated .efi files would still be in the same location.