Yes, you need the water to penetrate really deep down into the ground, not just wet the surface of the soil. So think of it as, say a 10 minute rain shower which would barely wet your driveway, vs. a 30 minute rain shower. Same as watering your lawn (if you have a lawn). You water deeply so that the water penetrates well down into the soil, not a little bit so just the top of the sod gets wet.
You can try it and see - set the sprinkler going and put your timer on for 10 minutes. Then go out with your trowel and see how deep the water goes down into the soil. Depending on how hot the weather is, and things like wind and humidity, it might take even longer than 30 minutes to water your pumpkins deeply enough.
I like the idea a lot of burying the leaf nodes to make the plants produce more roots, too! Never tried that myself. You'll have to remember to water the whole vine if they root along the length of it and put down a little fertilizer where the new roots are, as well.
