Paint me sceptical. What Mike Farkas has said stands to reason: In the third round of the POs you usually face opponents that are more difficult to score on than in the first round. Therefore the comparison is distorted in disfavour of players whose teams had multiple deep PO runs.
An examples:
Sidney Crosby has 185 points in 160 playoff games. 90 of those points (48.6 %) were scored in his 59 first round games, that is: in just 36.8 % of his overall playoff games. In the remaining 101 playoff games (second to fourth round) = 63.2 % of all games, Crosby scored 95 points, that is: 51.4 % of his overall PO production.
In all likeliness, more deeper playoff runs for Ovechkin mean that his GP count (at 121 now) goes up faster than his points count (at 117 now) and thus, his rank among contemporary playoff scorers takes a dive.