The new grub splash screen has a transparent hole in the logo. It isn't noticable because the screen is black when it boots up, but it is there. Attached is a screenshot of the splash screen in feh.
Created attachment 122541 [details] Screen shot of grub in feh
This is just a side effect of the conversion and ensuring a limited number of colors. There's a png as well if you want to use outside of the realm of the boot loader splashscreen.