(maybe mesa-only) why is there a minimum velocity setting and what does it do?

I've got a four axis mill running via a MESA card and doing pretty well.  One thing that tripped me up is not remembering to open some of the AXIS settings during configuration so it had pretty high minimum velocity settings on all the axes.

What kinda freaks me out about it is that if I tell the controller to make an XA move where the X feed is below the minimum velocity but the A isn't, it'll just move the A axis and leave the X static.  That seems weird to me.

So why is there a minimum velocity?  What use does it serve?  Why wouldn't I set it to 0?
And, if I were to set up a two-axis (linear axes) move in which one axis was above the minimum and the other below, would it similarly just not move one axis?  Like
G21
G0 X0 Y0
G1 X250.0 Y0.1 F100
Would it only do an X axis move and silently give me a non-tapered part when I was expecting a tapered one?

Thanks for any advice or ideas on this.