Bruce, it's interesting you make the distinction between ukemi and
This is am important distinction to me though of course one could argue the two are interlinked.
I posted purely thinking of breakfall, which to me means falling to the floor at what should be completion of tori's (nage's) technique. As part of this 'breaking the fall' there are the basic rolls, impact reducing actions (hand slap etc.) and more specialised roll out techniques.
Ukemi has a different interpretation and I consider this to be the whole method of 'receiving a technique'. So from the first moment uke is responding to tori's action they should be constantly alive to every
movement and in 'contact' with tori to be able to accept whatever may happen whether expected or not (nothing worse than anticipating omote and getting ura!) Only then can uke truly be able to keep safe and (if your dojo does it) look for countering options.
Recently I heard ukemi described as 'the art of keeping alive'. I like this!
I haven't practiced other martial arts but do think I am lucky in that some of my more experienced colleagues (20-25 year'ers) have been brought up with a real martial approach and this provides the 'slamming to the mat' that you mentioned. Aikido is many faceted and to me it is important to remember where O Sensei took the roots from, even though harmony is the ultimate
So again - I can only offer my opinion that breakfall is an important part
of self preservation.