Purchased XIAO, received FEMTO!

Now this is STRANGE…

If I select the destination board as FEMTO (that is, as received), the power draw when running a simple arithmetic sketch is 8.2 mA.
But if I select the destination board as XIAO, the power draw with the very same sketch clibs to 13.3 mA !

I’ve noticed that in boards.txt, compilation flags are different between the two boards.

For the FEMTO, a "-DCRYSTALLESS " is added to the XIAO flags.

What does it mean?

Why does it cause a (welcome) lower power consumption?