That's a 16-year-old book. Might want to try the updates; from the most recent one:
"A lot of these cards have been found over the last decade, but mostly baseball. They were issued with scrip to promote Spalding products. The cards can be found with biography backs and blank backed. Handcut cards are known as well since it appears that sheets of the set were issued.
A few blank-backed strip cards with a very similar format have surfaced, attributed to Thailand. I believe that they are British made and destined for overseas"
Besides, the cards are similar but clearly not from the same set when placed side by side:
There's also the little issue that a Johnson card has never been found on the uncut sheets of the Spalding cards.
It's just a mistake by whoever sent in the card not knowing what it was and making an incorrect assumption, compounded by the people at SGC taking someone's word rather than doing some research. Doesn't mean it isn't a desirable card, just that the slab and the listing is wrong.