It's not "moving goalposts", really. There
were areas of the in-game map of Azeroth that were missing but were known to exist in the lore, before they were added to the in-game's world map. Those locations beins: Northrend, Kezan, Tol Barad, Broken Isles, Kul'Tiras and Zandalar.
And as for Pandaria, that continent further reinforces the idea of an "unexplored area of the map" considering that
it is literally an UNCHARTED continent that sits between the supposedly "charted" area that exists between Kalimdor's east coast and the Eastern Kingdom's west coast.
Why? Why would it be "ridiculous"? Did you call it "ridiculous" when the continent of Pandaria was described as being "uncharted" despite being almost the size of Northrend? Why would these "new continents" on the other side of Azeroth have to be "the size of Kalimdor or EK"? Seems like you're making that statement only to make the idea sound ridiculous.
It's also headcanon to state that those maps we see are "complete" when there is no statement that they are,
and there is evidence that it might not yet be fully charted.
Mmhm. Let me present to you Azeroth's globe, courtesy of the ones who terraformed Azeroth, i.e., the Titans:
That globe of Azeroth can be found in Ulduar. And do you see anything interesting, there? Yes. It's missing:
• Kezan
• Tol Barad
• Broken Isles
• Kul'Tiras
• Zandalar
Read above.
And that is irrelevant, because I'm not talking about the
map, but the
planet. The 2D map is jut a representation of the
charted area of Azeroth.
And a contributor to this idea of "other side of Azeroth" is the fact that when you boarded a ship to go from Teldrassil to Stormwind, the ship would go up Kalimdor and then ship close-ish to the maelstrom to reach Stormwind, instead of going west and circling around Kalimdor. Or when you took a zeppelin from Undercity to Orgrimmar, it flew close the Maelstrom, instead of taking the other way around.