Plus the 6, 7, 8, and 9 PM start times you suggest would require not two but four different channels so multiple networks with at least two options each. In this case that would mean no NBC exclusive for Round 1.
I agree that they could stick the starting times closer together to where there's a bit of overlap from Game 1 to 2, and then from 2 to 3 etc. But they're also trying to keep the late-afternoon/early evening time unclogged as possible since national, and particularly local, news programs are solid money making slots for affiliates. That's why the early afternoon game was on the network but the 5 PM slot was Peacock only.
Meanwhile, with the Padres also winning last night, that's now 14 series out of 20 best-of-three series that were two game sweeps and either 18 or 19 of the 20 where the winner of game one went on to win the series depending on the outcome of today's Braves/Phillies.