Hey, and welcome! I don’t think this is false advertising. As can be seen from Banking apps on Sailfish OS a lot of banking apps do work normally. All the banking/financial apps I have work normally (OP, S-mobiili, Nordnet, Mobilepay, Finnair Visa). All of the messaging apps I have tried work normally (whatsapp, snapchat, instagram, signal), all the public transportation apps etc I have tried work normally (HSL, Wolt, Bolt, Finnair, VR, Nysse, Moovy). All the work related apps I have tried work, except the Microsoft authenticator (Outlook, Teams, Epassi, Joplin, Nextcloud). I don’t know but lets say that 90-95% of android apps work. That is pretty amazing considering that phone isn’t android based. Could they have said that they don’t guarantee every app to work? Surely, but they don’t have any ultimate list of the apps that don’t work. Best ones are found from this forum, but they are community led lists where reports can be many years old. When thinking about marketing, wouldn’t it be quite bad to put label that says most of the apps work, but we don’t know which ones? About same apps work under AAS that work with any custom ROM and I don’t think android forks advertise that some of the apps don’t work?
Neat thing here is that you can use Aurora store to download actual apps from Google Play store anonymously. This is why so many apps work and the experience is similar to end user as just using Play store. And with MicroG you can fake most of the check regarding Google services. Only safety net isn’t working IIRC.