That is broadly speaking true, however, the wonderful deal Ryanair has done in Girona is less to do with AENA and more to do with Catalan pride pushing GRO as "their" Catalan airport , as opposed to that "Spanish /AENA" administered one in BCN. Hence Ryanair now have a Catalan tape for the safety demo on the PA & for some time now "Girona" stickers plastered all along the side of a few aircraft.
I believe the deal they did in GRO was very "favourable" and indeed it may be renewed & continue. Simple passenger preference would tend to suggest otherwise, however there are indeed other "factors" (read cash) at play here.