I am usually very pro Felix. However this is one of the worst things I have ever seen from US coaching. Felix hasn't come close to showing sub 11 speed in the past 2 years and didn't even run the 100 this season. Prandini has also displayed faster splits by a clear margin in 4x1 and 200.
Either Prandini has handoff problems or .20 seconds slower is worth any handoff uncertainties in the worst interpretation. The only other possibility I can think of is that Prandini was more seriously hurt in her fall at the end of the 200 at the trials otherwise this decision is a poor one.
If Mitchell was serious he would put both of them on the 4x100, he should have Mirolake and Tianna just replace them in the semifinals since Tianna is going to be doing Long Jump as well. Maybe even rest Bowie for one so she can focus on the 200. There are 6 fast girls for Mitchell to use and he can use them all and rest the ones doubling or tripling at the right time.
Maybe the girls should just coach themselves and forget Mitchell since they actually have more experience than he does.