I think he might be referring to the words themselves - 'rabbit' and 'pork' - in that, despite not rhyming, together they are nonetheless described as rhyming slang.
In my London accent “park” and “talk” do not rhyme completely. Park has the usual “ah” vowel, but talk has an “o” vowel (in southern England we would call this an “or” vowel but I suspect that might confuse you more).
As luck would have it, "pork" and "talk" are rhymed in the first verse of Ian Dury's superb song This Is What We Find. I suspect the rest of the lyrics will only add to your confusion, unfortunately.
My Canadian ear somehow corrects the "pork" and "talk" so that they still don't quite rhyme (though they're certainly close enough for slant rhyme)
I hear the "r" in pork even if it's less audible than it would be in my English. And the "a" in talk sounds a little more like the "a" I'm familiar with from talk than the "o" in pork does.
I can see /park/ and talk rhyming with a transformation like that (like a Boston accent), but the o in pork is a completely different sound. Going from pork to pawk isn't something I can wrap my tongue around.
