Thanks @Drew-r for confirming these niggling disconnects between physical labels on instruments and graphic illustrations in guidebooks/sheets.
For all that, I had no trouble registering my new P-515 and the LP-1 on the Yamaha site. Once it was made clear to me about the serial number being a 4-alpha/5-number sequence of the digits, that solved it.
Although I understand the relaxed dismissal of the registration process as not much more than a hook to SPAM, I can also imagine a dispute scenario over whatever issue, x,y,z, and the big bullshitting bullies pointing to one's "obvious negligence" in failing to register their product as "yet another reason to reject supporting your claim".
I'd note too, that I stumbled across a Yamaha page where serial numbers actually had a functional purpose in identifying vintage acoustic instruments and their various provenances.