Is it "customary practice when selling a house that has tenants" to have a lawyer send a letter of eviction to the tenants?

Not looking for legal advice here, just some knowledge/experience, especially from Real Estate Agents. We’ve been renting a house in NY for over 8 years. ALWAYS paid rent on time, mostly early, sometimes 2 months in advance, NEVER late even 1 time. Payments were cash payments to the absentee landlord who owns the house. At the end of January we gave 2 months notice that we were moving so the landlord decided to sell the house rather than try to rent it again since she is now physically disabled & her parents are elderly. Due to her disability, house ownership was recently changed to “FamilyName Trust”. We have been beyond cooperative with the realtor in showing our home & holding open houses, bid was accepted, house is in contract. We received the following in an email from the Realtor: ” [landlord’s] **lawyer must send out a letter of eviction. we know you are moving, but this is the customary practice when selling a house that has tenants.**” I am shocked & very upset since letters of eviction, as far as I know, are to throw out a tenant for not paying their rent and we’ve always been early paying our rent & took great care of the house since we’ve been living there. BTW, we had a lease for the 1st year only so there is no lease needing to be terminated, and we did give a letter stating our move out date (1½ mos later than we originally gave notice for in order to give her more time to sell the house).

Sorry so long… thanks very much for your time in reading the details & for your time in responding.