Him being like that is his characterization.
It comes with an asterisk, and not an absolute rule, yes. People might be disappointed about it, but this was already apparent when we saw the flashbacks pre-Marineford and saw WB more caring about Ace´s safety than taking revenge on BB at all costs, it´s consistent with that at least.
But they were all dead, that´s the difference, at least presumed to be.
WB´s sphere of responsibility, first and foremost, is his crew, nothing else.
And family is something you create in One Piece, not born into, i think this has been made abundantly clear.
And if we spin this even further, something that was stated several times, WB was also someone who always considered his role within the world and his function of basically holding the reins of the New World.
He mentioned this in Marineford, Doflamingo stated this in his throne speech, he was a fundamentally different type of pirate than Roger was.
So yes, i see a very clear distinction between "let´s go save our mate who is alive" to "let´s go avenge the dead".
