For a little more context, see discussion at https://github.com/googlefonts/noto-emoji/pull/213. In particular note that this design upstream (i.e. in Noto) is actually motivated by a need to be consistent with Apple, which made the change from pistol to water gun about two years earlier. In this case Apple has effectively dictated their own standard that contradicts Unicode, and forced other platforms to follow. Practically all actively-maintained emoji fonts are using a water gun glyph for U+1F52B at this point: https://emojipedia.org/pistol/.
Anyways, what did you hope to accomplish by filing this bug against a Debian package? Is Debian going to start designing its own hotfix glyphs? If not, you should try to get this fixed in Noto (unlikely, admittedly) or use a different font.