I am not able to provide a solution but curiosity got me digging for info for a few minutes:
The lore on this is that DMI/SMBIOS data is a board-maker defined capability, which some provide user-access support and others don't. The way it's supported (or not) is completely up to the mainboard maker and BIOS supplier.
Look for a stackexchange.com article on "How to Change OEM Vendor Info" which surveys the topic.
At some point, you must have wittingly or unwittingly used a tool that can write DMI info. Maybe you chose that board because at that time hacks depended on this capability? But then, if you knew that, you wouldn't have to ask questions here?
I saw a Windows tool called RWEverything, which is no longer maintained, and it looks like it has a steep learning curve, but if nothing else the thinking might lead you to additional resources. Clearly there is a culture that groks this stuff, but having been a regular on this board for a year, I haven't come across any discussion about it.
While searching I came across hackintosh articles from Pike's Universum, for whom the WEG "pikera" boot option gets its name... Since OpenCore, and the modularity and ease with which it and supporting modules offer to hackintoshers, it looks like a the level of lore you need has been sequestered. Might need to learn google search tricks to uncover old lore.
