A Questionable "But"

Over the years I've learned many things from John Piper, and have for a long time received some of his regular emails. Just before our 30th anniversary, one weekly message dealt entirely with recognizing a couple in the church on the marking of 30 years of marriage, 20 years of formal ministry at Bethlehem Baptist Church for him, and 10 years of such ministry for her. In the middle of the piece I read this:

Their ministry has always been a partnership. There is no doubt that David is the head of his wife as the Bible says he should be. But he holds this woman in the highest esteem, as we all do. And together they have led this ministry to levels of influence beyond anyone’s dream.

The word that hit me hard falls right in the middle: but.

But is a word that is used to join two statements that, while both are presented as true, have particular relationship to each other. One only says "A but B" if either one finds that B is not typically expected when A holds, or one wants to qualify A in some manner: A is true, but only in some special or limited sense, not in the broadest or fullest sense of A standing alone.

In this case, A is the assertion that "David is the head of his wife as the Bible says he should be", which I would think has to relate at least to Paul's instructions to husbands in Ephesians 5:25-30, which immediately follows his statement that "the husband is the head of the wife as also Christ is the head of the church":

Husbands, love your wives just as Christ loved the church and gave himself for her to sanctify her by cleansing her with the washing of the water by the word, so that he may present the church to himself as glorious — not having a stain or wrinkle, or any such blemish, but holy and blameless. In the same way husbands ought to love their wives as their own bodies. He who loves his wife loves himself. For no one has ever hated his own body but he feeds it and takes care of it, just as Christ also does the church, for we are members of his body. [NET]

It has always seemed to me that any man who fulfilled this description could hardly fail to hold his wife "in the highest esteem".

So why the "but"? Why not connect these two statements with "so" or "therefore"? Why does John Piper, or the people he is writing to, seem to expect that holding one's wife in the highest esteem would not be part of the fullest sense of being "the head of his wife as the Bible says he should", or maybe even unusual or atypical of such men?

Actually, now that I think of it, why even have these two sentences in there at all? Why not just say "Their ministry has always been a partnership. And together they have led this ministry to levels of influence beyond anyone’s dream."? Is partnership in ministry something that John Piper thinks his audience will find questionable and possible evidence of the husband not being a "biblical head"? Is the notion of "headship" that is popularly affirmed in Piper's church something that a sufficiently large group of readers would assume made "partnership" and "esteem" grounds for suspicion that this pastoral staff member is maybe soft on headship?

Now that would be a sad thing indeed. But that "but" sure raises questions.