"But the sauce tastes nice"
Unhealthy things often taste nice.
"adds calories"
British people have an overweight and obesity problem. It's worse in low income people so I don't see 'add calories' as a positive personally for the average person in the target audience.
"most recipes for tomato soup would involve putting salt and sugar in anyway"
not as much though I think, usually 'add sugar to counter the acidity if necessary' and 'season to taste'.
"performative stuff (sugar and salt bad!)"
Well, sugar and salt is bad...
I do understand all the general criticisms of her by the way, but I think washing the sauce off baked beans is actually a good idea. I personally buy the low sugar, low salt ones, but I suppose they're more expensive.