Its hugely patronising
I think most people, possibly that poster dont even understand what oily fish is, mentioning tuna was a giveaway (in its canned form)
A lot of tinned oily fish is the same fish and people dont realise.
Herrings, sprats, whitebait and kippers, all the same fish.
Pilchards, sardines - same fish
Salmon, different fish.
Trout, different fish (I cant stand it), still an oily fish but not really found easily or cheaply in the supermarket in a tin.
Anchovies, different fish
Mackerel, different fish
Eel, yuk, never seen it in tins but you can buy it in a pot, not often
So the vast array of 'foodstuffs' are pretty much samey and in any case, theres nothing wrong with that. Most of these have been mentioned in the recipes cited here.