Guess you a right Mick probably a mis-quote / typo by the author, as the spokes I have had on '70's Honda's will have the plating finish removed when dipped in phosphoric acid. Nickel would be a lot more resistant.
BTW when he sold his PP bike earlier this year, I looked at his Ebay selling history and he had sold the remains of quite a few NOS K1 750 seats (cover etc) so I guess, like me, he bought NOS K1 seats in order to get the base and stainless trim.
Cheers ... AshD