That's a good quote, and I have a hard time explaining what was going on here. We know that many worlds in Magyar and Alpha Crucis never joined the Imperium. We know that the Bootean Federation never joined.
They joined the Imperium at one remove; They joined the Solomani Sphere which was part of the Imperium.
So how could Margaret give control over territories she did not actually control?
Is that a serious question? How did all those European kings, queens, popes, and whatnot give control over territories explored and not yet explored?
And for that matter, why was the Solomani Sphere set at 100 parsecs in diameter? It extends far beyond any border of the First or Second Imperium, so there's no historical precedent.
The region was the Third Imperium's
only open border, many of the systems had been Imperial members for relatively short periods of time, and Terra only joined in 583 or thereabouts. There seems to have been a kind of institutional squeamishness when contemplating expansion rimward, which may not be surprising when you consider what happened to the First Imperium when it tried to annex a certain rimward system.
Cleon explicitly chose not to expand rimward with the early Emperors following his lead up through the Pacification Campaigns and beyond. Rather than expanding rimward, Martin instead chose to kick off the Julian War attempting to annex three sectors populated to various percentages by the non-human Vargr. The radius was probably set after squinting at the map and rounding off the distance between Terra and the furthest "pure" Sollie/TC colonies. Consider:
Margaret:
"No more discussions. We're granting them an autonomous region. Live with it. The question now is where the border should be drawn."
Lord Aye:
Are far rimward as possible.
Margaret:
Of course, but it can't be as small as the Sol subsector. There has to be some territory involved lest they choose to be insulted. Besides, we've many pure or near pure Solomani worlds some distance from Terra.
Lord Bea:
The Stooge Cluster is about the further concentration of near pure Solomani worlds furthest from Terra, your Majesty.
Margaret:
How far?
Lord Bea:
The furthest world is about 47 parsecs from Terra, your Majesty.
Margaret:
Make it a fifty parsec radius and adjust the display. Any rabidly anti-Solomani worlds within that boundary? Any worlds We wish to remain in control of?
Lord Aye:
Rabidly anti-Solomani? Just these...
Margaret:
Too few to worry about. They have to adjust, besides they'll still have the right to petition the Throne.
Lord Bea:
There are the Depots, research stations, various training facilities, and the like.
Margaret:
Just as long as We have more. They're going to need ships and scouts if they're to explore for the Imperium after all. Set the border with the fifty parsec radius and get the paperwork started. I want these bastards off Capital and back in the sandbox We've giving them by year's end.
I've long considered the creation of the Solomani Autonomous Region as a bit of policy meant to provide a tar baby and/or sandbox for the Solomani Movement. The Sollies were supposed to get bogged down in the day-to-day minutae of administrating the already Imperial parts of the region while also distracted by the "4X" effort to annex the non-Imperial parts of the region (something which was never completed thanks to the Aslan and Hivers.) Putting it simply, the Sphere was supposed to be a poisoned gift.
Of course, the smarter parts of the Solomani Movement knew all about the tar baby/sandbox aspects of the grant. They accepted the grant anyway believing they could "flip" the poisoned gift and turn the Sphere into a regional power base from which the Movement would take back control of the Imperium.
And they came close to doing just that too.
As for the differences between the 1105 map and the Wars map in
IE, they can be explained by diplomatic horse trading. Each side gave up captured worlds to the other that they felt weren't worth to trying to control post-war and, for various reasons, the 3I gave more such worlds.
Other differences can be explained as the results of wartime operations that couldn't be maintained in a postwar environment. The salient in Magyar, for example, could be the result of the pursuit and destruction of a Sollie fleet by Imperial force. The Imperium made deep advances in that pursuit and temporarily occupied many systems, but it never had the forces necessary to exert full control.