Worn seals tend to draw oil into the inlet port (exhaust port is under +ve pressure eh)
Looks like a ring issue to me
Paul (polly) did his in situ, but its a mission keeping the valves shut tho (he fed string down the plugholes iirc !)
And the rings are usually not actually worn, but gummed/trapped in their grooves (lack of oilchanges i guess)