This isn't exactly a deep mechanical oversight, but it's just so odd to me lore-wise. Fish Cordon Bleu drains 10 sanity on consumption, but most characters' examination quotes suggest that they enjoyed it (Wendy: "It's actually... really good..." Wickerbottom: "I'll happily volunteer to taste-test." Wigfrid: "My ally is a god among men." Winona: "Mmm! Love Warly's dishes." Wormwood: "Yum yums!")
You could ascribe it to the foreignness of a frog leg dish for some characters' cultural backgrounds, I suppose, but no one takes any sanity penalties from cooked frog legs or the Froggle Bunwich, which is a much stranger meal. What gives?