I have a 2019 Sunstar 29ve, and I had same question with my brand new coach, got into argument about it with the selling dealer service dept because they all but called me an idiot because I did not see what they were saying, and what the manual was saying to drain my fresh water tank
I ended up calling Winnebago directly, who said my manual was the wrong one for my my coach. They sent me a new one ( I love Winnebago); as it turns out, I have to turn on my water pump for the water to drain out those low point water drains. I thought it was crazy; but after 2 1/2 years I love it. It pumps it out fast.
I have two sets of low point drains with valves, one in wet bay and another under sink in outdoor kitchen.