The decision whether to point-press is partially based on the fact that there is a killscreen. But there is also some risk-reward analysis that plays into it.
For example if there is a 100% safe way of point pressing (leeching DK on the rivet screen), people may still point press with or without a killscreen. On the other hand, without a killscreen, it makes no sense to point press a barrel board. (The following #'s are just estimates for the sake of argument.) If I just run a barrel board, I have about a 99% chance of surviving and get about 8500 points. If I point press at 12,500 per barrel board, I have about a 95% chance of surviving. Now that's a 400%/5-fold increase in risk (1% vs 5% chance of dying) with only about 50% increase in points per board. Meaning I could clear 5x's as many barrel boards without point pressing and only suffer a 33% reduction in per board score. Makes no sense at all. Of course the other boards play into the decision making, but I'll leave that discussion for another time.
Now I don't know the risk involved in DK Jr. point pressing as well. I'd imagine it's similar. There are certain tactics (jumping sparks) that are nearly 100% risk free while point pressing other boards may make no sense given the risk/reward ratio. I could see someone jumping sparks without knowledge of the killscreen. But it probably wouldn't make sense to point press a chain/key board unless you knew there was a killscreen.
I'm going to stay out of the Calvin Frampton argument, because what people do doesn't always 'make sense.' So you could make an argument that he was point pressing just for fun even though it was illogical points-wise.