Never heard of this one. My automatic 2nd move on D pawn openings in c4

Agree with Peta that swap is best weakening blacks pawn structure

This is still a line, though Bxf6 is the more testing continuation, it does seem as though this move is inconsistent and Id exchange if I chose to play this line.

Would e4 not have been better

Think Peta's plan is too open up centre using bishop on long diagonal coupled with Ne4 at some point. White Queen's Bishop is a bit away from the action

Bringing Black's bishop of back rank would force white to do anything but now white;s Kt can only go to the edge of the board and another offside piece in terms of battle for the centre

Probably there was nowhere useful for the bishop to go. So he stays home. This pawn thrust forces the knight to the edge of the board. Like you, I foresee 'developments' developing in the centre, shortly.

That's not too bad - not great - but you're still in the game. Often a more reliable indication of how things are going is how the evaluation scores are trending. Of course, during the game, you don't have the means of assessing this.

Taking advantage of the fact that for the moment the WQ lacks protection.

Cant quite see the point of a3 as b4 will not be possible owing to press on c3 (after following Kt move)

I'm inclined to go with the machine on this: the Queen really did need protection in order to free the c3-knight.