It is a different calculus if you are an athlete coming from African/Europe in the first place (whether you're based there or on a training stint there). You travel minimally to this meet and then go to Pre. As opposed to going back-and-forth.
El K, yes Kipsang is racing/traveling a lot. However, it's not unprecedented for this to work. See Stewart McSweyn last year. It's just more unusual in this day and ago.
Thoughts on the fields:
W400H: Muhammad vs. Russell ~ no McLaughlin/Bol, which makes it a little bit of a letdown
W1500: Muir will go off as a big favorite, though she battled injuries indoors. Reekie also was shaky indoors. Hull ran great in the 3000 last week and might be able to pull the upset if the Brits are a bit off. Embaye and Welteji are in the mix as well. We'll see where Cory McGee is as well
M100: Yes a thin field, especially if De Grasse is slowplaying the season per usual. Bromell big favorite, but can he do well overseas? Bracy in solid form as is Jerome Blake.
M800: Are Dobek and Rotich going to contend this year after last year's medals? Good test with neither doing much yet. Mariano Garcia is the most intriguing after his indoor season, and then you have a bunch of could-be medal contenders in Bol, Rowden, Hoppel, Arop, Murphy and Kinyamal. Huge field, hopefully someone goes with Sowinsky so it's not sit-and-kick. Good to see how Jake Wightman goes as well.
W100: Thompson-Herah, Shericka Jackson and Asher-Smith to me. Thomas is a step down in the 100, but we'll see how she goes. Del Ponte was a revelation last year as well. Not sure how real Sturgis' 10.87 is.
M400: A terrible field for a Diamond League. Feels like this should be recategorized with Olympic 6th place Christopher Taylor (44.79 PB) being the favorite I'd guess.
W5000: Expecting Niyonsaba to roll though there are some good Ethiopians led by Taye.
M1500: This one is exciting — Kerr vs. Kipsang vs. Tefera. You also have a strong list of contenders to beat that top trio including Katir, Hoare, McSweyn (bounce back from last week?), Mechaal and Simotwo. Really strong field, which will set the stage fantastically for Pre. Kinda wish Wightman went here instead?
110H: Looks like Parchment's race to lose with no Holloway, Allen et al in it. McLeod maybe can rediscover his old form?
W800: Goule vs. Hodkinson and you'd have to favor Keely a lot. Hurta will be of interest to US fans. Is the 800 her event or the 15?