It was stated that Ueshiba couldn't be thrown. Thus it opens the door to what is the difference between taking ukemi and being thrown. Such statements need clarifying and appear contentious otherwise I would say.
OK, in case anything is unclear - nobody here ever said Ueshiba or anybody else never took ukemi.
Of course, anybody is capable of taking ukemi if they choose to do so. The can also roll around on without anybody being around for miles.
FWIW, Dan has taken ukemi for me many times.