For certification purposes they do have only one Vmca and that figure is published in the AFM and denoted on the ASI, for most light multi engine aircraft that is the minimum Vmca.
Its not actually all that's published is the blue line speed which is Vyse which will be above Vmca for both gear up and gear down hence more than one.
And V2 isn't your best angle of climb unless it satisfies the other criteria for segment 1.
So the statement
They are not, V2 is best angle of climb on a Perf A aircraft.
is rubbish. As a pilot you wouldn't have a clue how the V2 speed is defined by the OEM or what its limiting factor is but its more luck than anything else if it is.