You know, I am kind of torn on this. On the one hand, I 100% agree that milk is the most important thing and they can get all they need from that.
On the other, for some, at a certain age, I think they may feel the need for more. For example, I could drink milkshakes all day and get a great amount of calories that way, but it would not be as filling to my tummy as a baked potato for example (okay, that was a bad example as I would much prefer a milkshake anyway, but hopefully ykwim).
Kate is your guys age now, just breastfeeding, may eat a bite or two or something the whole day long. Def healthy and thriving, but I don't know....I am ready for her to start eating something now too. Riley ate very little solids until gone the year mark, and he weighed over 30lbs by that stage. I was hoping for more of a balance this time round, but she is doing what she needs to do, I guess!