In both cases I got the exact room I booked (Deluxe King in Sendai and Larger Corner King in Hiroshima) and in both cases the check-in person said that I wasn't upgraded due to room availability and couldn't explain the notification from the app.

And, yes, I've received many not terribly significant "upgrades" that I was told about -- like recently at Shanghai Marriott Marquis the check-in person was happy to inform me that we were upgraded to a higher floor with a view of the Bund. What she forgot to tell me was that the room was one of the smallest deluxe kings in the hotel. And the app didn't tell me I was upgraded in that case.

And, of course, there was the time in 2017 at Le Meridien Vienna where I got notified of a suite upgrade to an 807 sq ft Executive non-smoking suite showing on the website 5-days before arrival. The front desk manager had written me in advance and asked if there was anything she could do and I said if possible a suite upgrade. She replied and said "no promises", but 5-days before checkin the reservation was upgraded. BUT about an hour before check-in the room got switched to a small room right above the hotel entrance which just happened to be where the hotel employees took their constant smoke breaks. At check-in, I showed screen shots of the upgrade and based on the redness of the face on the employee and the apparently heated discussion in the back room, someone clearly had decided that someone else deserved the suite more than me without realizing that I knew I had been upgraded. In fact, not only did I know about the upgrade, I had already written to the front office manager thanking her for the upgrade as soon as I saw that I was upgraded. Needless to say, she gifted me a lot of extra points......but that is a totally different situation.