"doesn't apply on departure. I'll see if I can find the reference"
Untrue in the US. FAR 91.117 is where its published.
LAX is home for me. Its normal to be issued the maintain 280 kt clearance. ATC expects you to accelerate out of 10,000 to that speed. Some controllers say it the way you indicate, others will say "when able maintain 280Kts"