TOTAL GUESS, just to be clear: The TPIR staff used to submit a memo to CBS every time they were about to unveil a new pricing game, I've seen some of these memos. They'd be submitted to the network before they had fully locked down the name. ("Now...and Then" was originally called "Inflation".)
Since you couldn't just go to Price is Right Fan Wiki in the 1970s, she had to obtain a list from somewhere, and she may have asked a show for such a list, and the show just went through their stack of files and thoughtlessly punched out a list of names for her from the old memos. "Extra Digit" might just be Squeeze Play's original name before they noticed how the mechanism looked.