Topic on Project:Support desk
Yeah it is and it is also pretty helpless as well as confusing. All over the place we are referencing the master version of the respective branches as the RELEASE NOTES to consult for end users. However on master we always will have the note "THIS IS NOT A RELEASE YET!" unless the branch is obsolete.
Oh, so this happened again *facepalm*. I've opened a task about this: task T198180
To repeat myself from the last thread about this, you want https://raw.githubusercontent.com/wikimedia/mediawiki/1.31.0/RELEASE-NOTES-1.31 not https://raw.githubusercontent.com/wikimedia/mediawiki/REL1_31/RELEASE-NOTES-1.31. They are not the same.