He or she meant that Uppland could have had the power to unify Sweden.
Yes.
The areas of svear, around lake Mälaren, and Uppland as the strongest was one faktor in the unification process.
Götar, divided in on East and one West, was the two outher powers.
But they was not organize in king and serfs moor like a maffia. He how has best relations whit strong groups hade most power. If he did something wrong, he lost his power.
Some say that it was Götar that forced a unification. Some say it was Svear. Some say it was the church. A few say it was Germans that financed it too counter a strong Danish state.
I don't believe that the smal 'stats' is importen in thé process.