This seems very much like the way we do it. With less able ukes we would allow them to roll, and with more able ukes then something more akin to a flip is what arrives.
As Prof. Goldsbury has said...you are vulnerable to a takedown and you increase this risk if you bring uke onto you rather than ensuring you cut down to break posture/take balance first.
Equally of course, knee strikes, kicks etc are available in your defence as they would be to someone working against double leg take down.
So for some, as Dalen points out , everything else could be seen as fluff.
After all - a good initial irimi / atemi could negate the requirement for anything else perhaps.
Some may take the view for instance, that the real benefit of uchi kaiten nage is not as a technique, but as an excercise to practice the body movement for uchi kaiten sankyo.
This feels much more martial and removes the concern of uke letting go.
But again its only a technique...an opportunity to find something.
So others may argue that the real benefit of Uchi Kaiten sankyo is that it allows you to practice centre, distance, breathing, timing control.
But again ...these aren't the whole.
Others may argue that breathing , centreing, timing and distance aren't the best thing to practice.
For them irimi / atemi is where its at.
And maybe others may argue that there is more - a fusion of energies is possible.
and others may argue that their practice is in the mind. as soon as uke thinks to attack its too late.
Whats my point? Everyone looks at things with eyes that match their level. Almost to the point of seeing what they want to see.
As your Aikido progresses - if you are open - you move beyond physical differences and look for different things.
And that is the great thing about Aikido...just when you think you know something, someone comes along and re-writes everything for you.
Only thing guaranteed in aikido?
Others may argue....