`pkgdev bugs python:3.8` does not find "dependent" `dev-libs/mpdecimal` bug

[mgorny]

I've filed a separate stablereq for dev-libs/mpdecimal-4.0.0: https://bugs.gentoo.org/933560

However, pkgdev bugs doesn't find it and insists on merging dev-libs/mpdecimal into dev-lang/python stablereq:

$ pkgdev bugs --auto-cc-arches=* $(pkg):3.8 
Checking =dev-lang/python-3.8.19_p2 on 'amd64 arm arm64 hppa ppc ppc64 sparc x86'
Checking =dev-libs/mpdecimal-4.0.0 on 'amd64 arm arm64 hppa ppc ppc64 sparc x86' [added for =dev-lang/python-3.8.19_p2]
Merging @python/cpython group nodes: (=dev-lang/python-3.8.19_p2,)
Merging =dev-libs/mpdecimal-4.0.0 into =dev-lang/python-3.8.19_p2
Check for open bugs matching current graph? [Yes/No] (default: No): Y
Continue and create 1 stablereq bugs? [Yes/No] (default: No): N

gentoo/gentoo@f0b656f30560b253cde62a30bc9511b634525b89