Tokyo Shinobi Squad isn't doing that bad, it did better than first Kamio Yui volume if i remember well.
So Souma peaked in volume 14 and from there it didn't sell the same, so what? this happens with every popular manga, you know that, so why is just with Souma that is suddenly something so bad? did it matter for the next 16 volumes? if Tsukuda never made the big mistakes we would never have this discussion because the manga would be going on for the 8th year with no signs of rushed ending, it only became a issue after the big drop in sales with the time skip.
So a series that sold like over 200k for 7 years with multiple anime seasons don't deserve 3 epilogue chapters in a minor magazine? you're talking like these things are just so rare or special when isn't really something that special, and we're talking about Shonen Jump, in any other magazine Souma wouldn't even be finished yet because the editor in chief wouldn't rush a popular series like that because some drop in sales, Jump is the one that have the luxury of doing that.
I don't know if you realise but implying that a cooking series is so popular in the west that it's getting a new anime season because of that it's the definition of something impressive.