He did throw the line in....ever since Pepper people thought there was hidden messages and lessons in their records...by playing them fast, slow,backwards, whatever.
Since the controversy about who the Walrus on the cover of MMT was fairly recent he tossed in the line about Paul.
LENNON: "Well, I heard some Beatles stuff on the radio the other day and I heard 'Green Onion' ...no, 'Glass Onion,' I don't even know my own songs! I listened to it because it was a rare track..."
PLAYBOY: "That was the one that contributed to the 'Paul McCartney is dead' uproar because of the lyric 'The walrus is Paul.'"
LENNON: "Yeah. That line was a joke, you know. That line was put in partly because I was feeling guilty because I was with Yoko, and I knew I was finally high and dry. In a perverse way, I was sort of saying to Paul, 'Here, have this crumb, have this illusion, have this stroke... because I'm leaving you.' Anyway, it's a song they don't usually play."
I guess I was referring to it being a year later (69) when the real PID rumors flew....obviously there had been squealings as early as Nov 66 when Paul had his motorbike accident. That's what's John was talkling about. Which is what caused your confusion. Sorry about that, I wasn't clear.