You can talk about discipline all you want, but the fact is that the line for what is and what is not a penalty is not a line at all. Penalties are called when and because the refs want to call them, and that is primarily a function of the score, and 'who's turn it is' to get a PP.
If your team is leading, you are more likely to be called. And the larger the lead, the more that increases. This article shows how game management affects the frequency of calls, and how that is more pronounced in the playoffs:
https://soundofhockey.com/2021/06/12...-the-playoffs/
Discipline has little to do with it.