This is completely a fan's interpretation, and shouldn't be counted as to Touhou canon.
The Problems with Snail Aging
The gag reel shows Patchouli during one of her rare outings, and having to adjust to her declined health. In order to not draw attention to herself, she's been wearing contemporary clothing for the occasion. Throughout the travels she's seen as a generally odd person amongst the normal townsfolk of the human cities, due to her young looks and odd colored hair. Odder still from acting like a woman who's over a century old. Amongst other cases is her inability to climb stairs as efficiently as she did about six to eight decades prior, as well as lecherous men flirting with her for her looks. The whole reel is for a tongue-and-cheek playfulness about how Patchouli is still surprisingly mobile in Black&White, let alone Hisoutensoku. Along with the usual scumbag lech over-stepping the boundary, to get his teeth knocked in.