I'm not an Apple person but IIRC their appstore is functional for already purchased and free apps. New purchases, as well as import of devices, are done via various grey schemes like via currencies and borders of third countries. I can't recall news about someone getting individually banned for that, but some opportunistic foreign banks closed their doors to rubles fearing sanctions. Official stores are closed, but I guess their repair\replace services are still operated but without a connection to the Apple themselves. There were also services to install non-Appstore banking clients and government's services via some loopholes. At the same time, except for the app in the OP, some apps can choose not to be availiable in a select country on their own.

I guess Apple did the formal exit and then stopped to care. It's not operating in Russia per se, but it operates in other countries with entities barely passing as legal consumers and resellers. They still get their profits as usual, and these interlayer smugglers make big bucks enough to be advertised in every second russian youtube video. Is there then a mechanism to make Apple filter them out?

A bit related news piece: russian gamers cried over Sony limiting Helldivers 2 to select countries, while other russian gamers dunked on them for they have PSN linked to the right country.