I did a quick web search and found many takes on planting on hills.
The most common one was to plant seeds in groups not on an actual hill.
The next was a hill had a flat top and a mound had a round top.
Some people said it was to help warm the soil this was the one with the flat top.
One was to keep plants out of the water.
And so on.
No wonder people are confused.
This is my life long experience in Texas and other places.
Hill/Mounds would dry out too fast and I would be watering them all of the time even if surrounded by damp soil.
When it rained the soil would wash off the mounds and leave to seeds exposed.
Through my laziness I discovered the best results for my environment was to plant in rows slightly sunken.
Then as the plants grew mound up a dike on both sides about 18 inches apart and let water run down the trench.
For some reason people move here and bring some very bad practices with them.
For the most part you cant talk them out of it and blame it on Texas.
Then they look at me and say I dont know how you do it.
I tell them that I have told them how and their reply is that isn't the way you are supposed to do it.
I remember we used to put huge dikes about 8 inches high and 6 feet across around all of the "groups" of melons and fill them with water.
It worked great.
Worth