The answer to your question is the entire point of the blog post, which was written by Guy Steele, who worked on the original design of Java.

Smalltalk, the grandaddy of OOP languages uses idiomatic functional programming for its messages.

Some languages, such as Scala, have a mix of FP and OO concepts. Some FP features make use of TCO, so this helps to make them a first class citizen.

Oh yes, my mistake.