Me, too, but my answer is always the same!
With two lines 180° out-of-phase with one another (the left-hand BS7671 diagram), most electricians in the UK seem to call that "split phase".
I can't say I've come across 'anti-phase', but, in my opinion, to use "single phase" for such a supply is just plain confusing/misleading, since there clearly are two 'phases'.
As far as I am concerned, any 3-wire supply which has two lines which are out-of-phase with one another is "two phase", whether the phase difference is 90°, 135°, 180° or whatever - 180° is merely one possibility out of a continuum of possibilities.
Kind Regards, John