A variac is a variable transformer, it can do nothing with regards to compensating for the sag that occurs in an AC line when the equipment connected to it draws more current than the mains can provide unless maybe if they’re including some form of AC regeneration in them now since I know that kind of device is available to hobbyists but I don’t know how if at all that would compensate for the sag.
This statement appears to ignore the quote which immediately proceeded it. No need to repeat myself. If you don't have a variac in your measurement arsenal you literally can't make accurate measurements of high power amplifiers. Its a rare amp that can't run on a 15Amp AC line!
my original premise which you refuse to address.
This statement is false on account of the word 'refuse'. What is the matter of which you wish to discuss? Regarding your innuendo following this statement, its false as well, based on what appears to be a made up story.