It appears Sweet Synthesis is also marked "That skill is too old for this path." while not appearing in standard.php. (So much for getting a huge bowl of candy for halloween.) Never received any kind of response when I reported "Fifteen Minutes of Flame".
Apparently, standard.php just can't be relied on as being accurate.
The main issue is that you keep blaming standard.php when that has nothing to do with it. Mafia actually checks standard.php?date=(year-2)-01-02 (because I noted years ago that standard.php isn't very reliable for December stuff), which does correctly show those skills. The problem is that the skills are on charpane.php.
I already wrote removeAvailableSkill years ago, when the Unpermery was around. That could probably be used to "forget" these skills, though that requires checking the exact timing of things being handled at login.
To preempt skills being listed one at a time over the next few months, typeii.php gives the list:
Ceci N'Est Pas Un Chapeau, Fifteen Minutes of Flame, Gingerbread Mob Hit, Licorice Rope, Stack Lumps, Sweet Synthesis
I did see your bug report, and brought it up in /dev. I guess I could have responded with "this will probably never be fixed".