Explaining different nutritional requirements is a fun one, I remember having to explain it to my kids when they were 4-8, as while we see eggs as "healthy", they were seen as "unhealthy" for one of the friends they at at the time as said friend was anaphylactically allergic to eggs. I don't think it took as long as it could have to grok as we knew quite a few families with differing dietary requirements (gluten free, vegan, various food intolerances etc). Meanwhile we were lucky not to have a lot of food intolerances (only one was food colouring with youngest) so had just stuck with stereotypical "healthy" and "unhealthy" XD
I like that you brought up that questionability here.
That's some nice colouring in :D
With kids they're going to go on and off foods as they age and it's going to drive you nuts for a bit where a previous favourite thing ever is suddenly yuck. Just gotta keep offering whatever is healthy for your current diet/stage and hoping XD