Interesting. How did you get that?
FP3 stable 1.5-r seems neither available for manual install nor OTA currently.
Q to R OTA upgrading for FP3 was also not announced as available at Week 44, 2022 : Development and Testing Updates.
Are you in the testing group for this or were you running a special dev build for testing out a fix for an issue? (I saw the updater of such a build offering a Q to R upgrade once, when it shouldn’t have been available officially.)