Its presence implies that the company both is capable of and is overcharging the people coerced into the higher price tier.
"Overcharging" is a concept without a precise meaning. The SSO-capable version has a feature that cost money to build and support. That it is sold at a higher price (often alongside other enterprise features that cost money to build and support) is not proof that they are overcharging.
Any company that is tying to recoup the costs of building those features will charge the customers that use those features. The existence of a price differential between the 2 editions does not tell you whether they are overcharging.