The regression-update tag is for bugs that did not affect the version of the package in the final release, but do affect the version of the package in the -updates pocket. So it is specifically for bugs introduced by Stable Release Updates.
The regression-update tag is for bugs that did not affect the version of the package in the final release, but do affect the version of the package in the -updates pocket. So it is specifically for bugs introduced by Stable Release Updates.