I’ve done this as well when the first in the order is sprints with a sled.
Regarding the hill; however, I think there’s something to be noted in regards to training effect:
Here’s my thoughts- how consistent is the actual overspeed effect of hill work then flat in the same session. If it only improves, for instance, a 30m time by a small margin, and only once in a while (ergo not every training session), then how significant is the training effect versus reversing the order?
I’m not against it, as I stated I’ve used sleds first then unloaded sprints; however, I think it deserves further scrutiny if this particular order of events is to be considered to be the more favorable one.