[visarga]

Counting items by value is a maximum likelihood estimation method too. It's still ML if you do a count, group by, max or threshold - just a less sophisticated way of doing things. The Naive Bayes algorithm is implemented by counting, at its base.

[anothergoogler]

So any reduction is ML?

[visarga]

Only if it fits to an existing statistical model.

[anothergoogler]

How about counting the elements of a linked list.