Yes totally agree grub4dos for UEFI name was very bad selected, and even on http://bbs.wuyou.net...read&tid=422652 where the developer started the topic, many people prefer to call it G4E.
it was devoped to be used ONLY under UEFI environments, not to boot UEFI images from a BIOS only PC.
G4E can't use an equivalent to grldr.mbr (as old grub4dos does on Bios) on UEFI PCs because of UEFI design, so it do not exists, but there are other ways, I will not talk of them as your concern is about Bios only PC.
A PC can only boot in accordance with its Bios/firmware, if it is only Bios it will not be capable to boot as UEFI.
Bios programs do not have the required code and internal drivers to boot on UEFI environment, Bios programs are very small and older than UEFI firmware, so UEFI was not developed yet when they were written.
UEFI firmwares have the required code and internal drivers to boot on UEFI environment, and on the contrary are big enough and can content also Bios code and drivers required to boot on Bios/CSM/legacy mode.
But many new OEM PCs are now only UEFI, and there is no more an option to select Bios/CSM/legacy mode, then is when G4E or grub2 can be used as we used before old grub4dos on Bios PCs.
From my post No. 288
If the files you want to boot are:
1 - WinPE ISOs or WIM files based on 8.1 or newer, and as long as when made they were prepared to boot on Bios and also on UEFI they will boot on Bios or UEFI PCs.
2 - In the case of Linux ISOs mayority of them are capable to boot on a Bios/CSM PC or on another UEFI PC.
3 - If you want to boot Windows VHDs on a Bios/CSM PC or on another UEFI PC they have to be 8.1 or newer, for a wimb's program to help you make all things almost automatically see: VHD_WIMBOOT it contains also a PDF file with detailed instuctions.
NOTE: Win 7x64 is not fully compatable with UEFI.
The files you are actually booting (using grub4dos) on your Bios only PC, that you think are UEFI only, very possible meet the conditions mentioned on the quote so are bootable on Bios and on UEFI environments, and in your case they are booting on Bios mode, they NEVER could boot as UEFI on a machine that is Bios only, it is not possible, as Bios lacks all required for this.