The policy states:
So, post sincere-looking questions (you know, the kind that invite answers) that: ... misinterpret a real Torah concept or Jewish text ...
I can't speak for anyone else, but for me, the issue here is not whether Judaism ideas (i.e. "Torah concepts") are fair game for PTIJ fun, but whether "gefilte" is an expression of Judaism (and not just of Jewish culinary culture). If it is, playing with it is on-topic. If not, then it isn't.
Consider the following parallel examples, all of which I would consider off-topic (and, for the record, not funny):
What kind of key do I need to open lox?
Does cholent taste as good if pot is substituted for potatoes?
Is everyone who goes to NYU impatient? The school's name sounds like "nu!"