I've gone out to dinner with my mother and long-term friends, but I'm not dating any of them. Sometimes eating is just eating.

Emphasis on with your steady partner

My steady partner is a long-term friend. Not everything is sexual or dating just because we are, in fact, in a relationship that includes sex.

Sometimes eating is just eating.

Going steady is commonly understood to mean a long term , serious romantic relationship

Being obtuse and choosing obscure definitions of terms to win points on technicalities isn’t clever, it’s childish

I do know what it means. That doesn't mean that everything done while in that relationship has anything to do with romance. Sometimes eating is just eating. This isn't making up definitions. It is acknowledging there is a vast difference to what folks call "date night" and stopping to eat on the way home from a destination. Sometimes eating is just eating.

Calling me childish for having that view seems childish in itself. I'm simply not romanticising everything.

Semantic arguments are childish