Re: Article: Taking Ukemi and Being Uke by Peter Boylan
I like to see shomenuchi as uke's defense to a pre-emptive strike to the head from tori.
If tori's timing is perfect, he will knock uke in the head and it is over.
If tori is a bit slower, uke will be able to defend his head by raising his arm, when uke's balance is broken, go through with omote.
When tori is even slower and uke's balance is not broken, you might have to go for ura (depends on the energy of uke).
If tori does not have any clue about the pre-emptive strike and is waiting for the first strike of uke, he can expect something else then shomenuchi.
Just my thoughts on the subject