What did eventually work for me was using the following path:

grub2-mkconfig -o /boot/grub2/grub.cfg

I'd actually resigned myself to using the rEFInd boot manager, as I'd used it in the past, and I'd read that others had better luck when implementing dual boot systems with two OS's both using EFI. I had that all working when I decided to to have a closer look at how grub works, and used the path applicable to my system. I didn't even have a grub2.cfg, and I have read today that others have also had this same issue after resizing Mac partitions. I'm just glad it's working as I want now.