The way I figure it, when the original V10/V12 for Fuel was made, the price of RAM was such that there was an advantage to going with two types of RAM as they had done with the Octane V12's. As production continued, RAM prices fell, and it was cost effective to just go with the higher-density stuff, and build out to either a V10 or a V12 - this also meant that in production they only had to stock one set of parts and could build either way depending on demand much later in the manufacturing cycle. The resistor could be added or removed from the BOM at the time the production order went in, and the ID strings were programmable.
As a note, I too was poking around in the kernel files, and note that there is only one set of BUZZ microcode that get's uploaded. With all of the 'types' of V10/V12 part numbers out there, I can't actually imagine that they can actually check by part number, as a V12 is a V12, early or late vintage, and indeed poking through the Odyssey driver binary I didn't see anything obvious. If past history is any indication, I wouldn't be suprised if it was just the 'amount of reported memory' that determines to the system whether it's a V10 or a V12.
I have 2 V10's here, one with the old-style 32MB SGRAM, and one with the Samsungs. Guess I'll have to warm up the soldering iron tonight...
Addendum: Looks like in Hamei's photo's, the PCB part number is the same between both boards. I know the 'old-style' 32MB boards are different (they also have a 'Made in Canada' under the part number) but since the newer boards use the same PCB, it looks really promising...