Hi,
The problem is that different machines are different as far as Bios goes.. There are several companies that write Bios for manufacturers, some of which then modify them to their liking.. Some manufacturers may write their own..
It is a function of the Bios as to whether a CD\DVD drive is recognized as a UEFI CD\DVD drive..
A CD\DVD drive is not configurable as UEFI Specific.. It is a function of the Bios to allow selecting it as a UEFI device primarily for the purpose of installing Windows as a UEFI installation..
A Flash Drive may be recognized as both a UEFI and Standard (Legacy) device.. Some of this is determined by the file system and GPT\MBR designation.. All of the stuff being discussed from what I can tell, is simply a failing of the way Bios was coded to function in a logical fashion.. Or not function..
The Lenovo laptop is a perfect example.. Their support site specifically states that Legacy Media is not recognized as a valid boot device when the Bios is set for UEFI.. This is due to an incredibly narrow minded view of the world as far as computers are concerned... A Bios update may improve the situation if Lenovo so desired..
My main machine is 8 years old.. It was UEFI capable long before I had even heard of UEFI Bios..
This machine automatically switches from Legacy to UEFI and Vice\Versa, depending upon how it detects the connected media..
I should note that my CD\DVD drive only appears a a UEFI CD\DVD drive when a Windows Installation DVD is inserted... That again is entirely dependent upon the function of the Bios.. Some machines work that way, and others simply will not allow the use of a Windows 10 Installation DVD for a UEFI Installation..