I know this has been a while on this thread, but...
You might ask them to cite their reference. And then read it yourself. If you feel there's room for interpretation you have a representative government - take it up with them. Worst they can say is 'no' and then you can get in touch with your state and federal representatives.
I'm not trying to cause any hate here. But their blanket statement that (all) SF-97s for those vehicles state they're for off-road use only is false. Some SF-97s may say that for one reason or another but not all. I've personally obtained an SF-97 for a M998 which I then went on to title in VA for on-road use (granted as an antique). No where on that SF-97 did it say anything about off-road only.
And if I had wanted to go through the proper processes to title a M35A3 without any documentation other than a bill of sale, that would've worked too. (which might be a course of action for you)
And lastly the bit about a non-standard VIN is, IMHO, just bunk and heaping on nonsense. There are, again IMHO, plenty of nonstandard VINs out there.
I know laws vary state to state. But please, do not accept such FUD as an answer. Do the research, put in some effort, and get it done.
Good luck,
SJ/JD