Yes, there is also the case of buying an advisor from Poland player, when Poland has the dynasty that allows advisors on wonder spaces.
If Rustan confirms your interpretation for Chopin I will apply it in this case too.
Confirmed by Rustan. I have just uploaded the fix and now Varangians effect is applied when buying Chopin from another player or advisors from Poland wonder spaces.
(I can't think of other possible cases, if I'm missing something just let me know).