NymVPN disallows a user to select the same server for entry and exit, but yes indeed, there is the additional problem that two different servers might be run by the same operator - and thereby undermine the benefits of decentralization. This is why Nym is rolling out the concept of ‘node families’, so that the route selection algorithm can detect if several nodes are run by the same operator and make sure to exclude those routes. (The concept is somewhat similar to Tor’s relay FamilyID’s: Tor Project | Learn how to configure your relays' FamilyID).
Current status: Nym Node Family scheme has been conceptualised and is now being scoped for technical implementation. The scheme will be presented and explained in an Operator Town Hall soon, so if you want to know more, and especially if you are also an operator, do keep an eye out!
In the meantime, we urge users to select nodes from different operators where obvious. Do feel free to ask more questions!