devtrackers.gg
Apparently it was there right before release but they got the load time down and therefore it was no longer necessary
Argonomic is a designer on Titanfall and Apex btw. :P
And you've got it right. There were several iterations of the "staging" area was, with the Training area being the final iteration. Ultimately, it was not needed for matches as most of the map loading is done in advance of matchmaking and and only a few seconds needed to swap out lobby bits.