I feel like we might be in the same situation somewhat. I'm signed up for USPS Informed Delivery and I can see that we're receiving a letter from the TSC today.
Case status on USCIS's website says: "As of May 25, 2019, we completed our review of your fingerprints and are working on your Form I-751"
Case status on the My USCIS website says: "You do not need to do anything at this time"
Tracker app says: "fingerprint review was completed"
My wife also received a notice that they would reuse her fingerprints and that there was no need for a biometrics appointment. It's nice to see progress actually happening but it's kind of a bummer to be told that it was a mistake now.