this is only applicable to federal contract workers, as I understand it.
am I wrong in this interpretation?
Officially, yes.
Unofficially, wrong. Most union shops will force their wages up indexed to the fed wage.
Recently a local city council mandated that grocery stores had to pay "hero pay" to their workers - easy to do when it isn't YOU that has to pay the extra wages - supermarkets run on a 1-2% profit margin:
The war began when the L.A. City Council passed a law mandating that grocery store workers receive a temporary “hero pay” $5-an-hour salary bump for 120 days to compensate them for working during the pandemic. Supermarket mega-corp Kroger balked, and its execs decided to teach L.A. a lesson by closing two of its Ralphs supermarkets (Ralphs is the dominant grocery chain here in SoCal).
David Cole explains it better than I ever could here:
https://www.takimag.com/article/hand-in-hand-to-hell-the-black-jewish-alliance/
So how can biden change the terms of a binding contract?
No need to ‘interpret’, as that is EXACTLY what was typed.