We know that referees are very reluctant to give power-plays in the playoffs. Right? Well, maybe not:
Remember, these are just power-play opportunities - coincidental penalties and fights do not count. Overall since 1987-88, there is a slight increase in penalty calls during the playoffs:
Note that I'm missing the regular season for 2002-03. Long story. Anyways, the problem is that this overcounts the first round of the playoffs - perhaps there are fewer power plays as we get further into the playoffs?
Power-play opportunities tend to drop off 25-30 games into the playoffs, roughly in the 3rd or 4th game of the opening-round series. Splitting the playoffs at the 25-game point gives us:
Now it's possible that there are fewer penalty calls in the 3rd period or overtime of close games. We don't have that data dating back to 1987. But it's possible that there are just more people watching close playoff games than any game during the season, and so more people are aware of lax refereeing. In general, there barely any fewer power-play opportunities in the later rounds of the playoffs than there are during the regular season.