It really is cutting it short. Anything that pops up will be very small. Some seeds will not sprout or will be spotty sprouting because they might like it a bit cooler to germinate, and some may not germinate at all if they need a cold period.
So make sure they are fast warm temperature germinators.
Remy

I just planted kale and collards.

Even something that sprouts in 7 days or less will still only have a couple/three weeks' growth by September 10. I don't know of any seed that will grow fast enough to have much top growth in that amount of time. Even my balloon flowers are only an inch tall and I summer sowed them the third week of July.