netgen's LVS compares circuit topology. When there are symmetries, there are multiple devices with similar connections that can't be distinguished by topology alone. For example, in your circuit you have 2 transfer gates that are topologically equivalent. These symmetries are also known as automorphisms (a term from graph theory, I believe). In order to resolve these, netgen will first try to differentiate the circuits by devices sizes and if that doesn't work, then by pin names.