No, not a typo, buttermilk milk.

In a recent thread about pancakes I mentioned I use powdered buttermilk
in the mix. It works well, and I make the dry mix for four batches at a
time. To the try mix, I just add eggs, melted butter, vanilla extract
and water to reconstitute the buttermilk.

Today, however, I found myself in a recent Julie situation. More milk
that we could possibly use before it goes bad. Rather than adding
water, I used the milk. They came out lighter and fluffier than usual.
I'll do it all the time now if we have milk in the house.