ATC can assign altitudes that are wrong for direction of flight.

This is true. The "East is least and West is best" only applies to VFR
flight. A good example is when I was flying East at 6000 and ATC instructed
me to climb to 7000. I was IFR at the time. I started picking up ice at
7000 and requested "lower". ATC then cleared me back down to 6000, not 5000
which they could have.