the way the schedule sets up, 1500 all rounds is done the first half of the trials, 5000 all rounds is second half of the trials after 2 days off. so he guns for the obvious. something goofy happens he makes a go at 5k. if you don't declare you can't circle back to it if the unexpected happens.
i expect the same on valby. she goes for the 5k first half of the schedule, all goes well, scratch the 10k she doesn't like. if there's a misfire, she's technically entered in the 10k. they won't just let you "panic enter" the second after the first goes badly. so you have to enter and keep it in play.
for contrast, lavrone's 400H is same days as the 200, it'd work with 400, but that might tire you out. in any event, she's bailed on all the Plan Bs and maybe assumes worst case if something weird happens USATF names her to relay pool. but part of the deal is her Plan A is literally the last event last day on the schedule.