Tired
I'm not having a go at you, honestly.
ATC has the expectation that the pilots they are controlling will know regulations appropriate to the airspace they are in. With regard to the 280 kt thing, they expect you will comply out of 10K. Not ambigious to them. I can understand someone who doesn't ply the skies here to question it (understandably so), but how many standards need they conform to?
As to time/alt of issuence, I can only imagine they are trying to stay ahead of the game. The clearance is no more than a small number of minutes away from being acted upon. When I receive an approach clearance for the ILS (assuming all other considerations are met) I mash the appch button on the panel. I don't wait till the loc is alive for fear of missing it because I wanted to wait. Perhaps out of 9 or so is when the controller tries to hand you off to the next controller, who knows.
You and I strive to be ahead of the plane, imagine ATC does the same.