Kill a first responder with your contraption after a crash, then have the lawyer you've retained for $25k convince a jury that he'll stipulate that you are the builder, you are the designer, you made the decision to ignore the CFR, you are the assembler, but you are not the manufacturer (because you are trying to loophole your way out of the CFR) of said culprit vehicle.
There is NO reasonable (what juries and judges do...they reason on facts) explanation as to why the 60V rule would not apply to a DIY electric vehicle operating on a public road or highway. None. You are all trying to rationalize why it should not and a judge ain't gunna buy your shit to get out of a negligence/manslaughter legal proceeding against you, the manufacturer. The only difference is a manufacturer offers goods for sale. Is that enough to get you out of killing someone? I don't think so.
You also stand a much better chance of getting extracated if you are in the local fire department's records as FMVSS voltages compliant, versus having firefighters stand around, smoking a cigarette (something you can't do around a crashed gasoline car) until they toll the time for your battery to self discharge below 60V. So, just before you pile into that telephone pole, turn on your electric cabin heater..