All sounds a bit metaphysical to me. Not so long ago a ju-jitsu person (I presume - 'cos it wasn't anyone from our club!) put someone in a standing pin (a bit like reverse ikkyo - katagatame?), prior to smashing a bottle over the back of their neck. Though you may consider this a lesson in the difficulty of teaching martial arts to those who will use it inappropriately, the first thought is, why didn't they roll out of it. Ukemi can be a very useful way of escaping technique. In fact a prior ukemi is an excellent way of escaping many techniques.
I'd also say that ukemi teaches us that we can blend with something as big and hard as the earth.