What Boris does with ambience is to give it vocal apparatus; a human voice. Not content to simply play in a new note or texture, he often applies voicing to the attack and development of the sound. So much of the music thereby ends up feeling warm, organic and almost vocal.
(The master of this of course is Eno - just listen to Reflection or -
as this album reminds me - Thursday Afternoon, for how much interest can be brought to a few notes).