GGB - I do get the playful comment about EWP, and told you why many of us bad mouth it. On the other hand, I still have a couple. All mine are still smooth looking young trees, with long needles and not much ramification. Lost my oldest one last spring. I love the look of a mature one in the wild. So I keep playing with them.
If someone figures out how to handle EWP in a way that will make nice bonsai, please document it and let us know. Vance figured out Mugo, maybe you'll be the guy for EWP.
Back Budding debate. Just as you have Yatsubusa varieties of JBP and JWP, there are many different cultivars of EWP. There are a few named ones that do pop epicormic buds. But I forget names, one of the named weeping EWP is famous for this, Not 'Pendula". It is also possible that one has picked up a chance seedling or plant that by happy accident is one of the atypical EWP that is able to back bud. I don't doubt it is happening. I just chalk it up to a unique combination of the plants genetics, the culture it receives and the climate it is in. In otherwords "RESULTS MAY VARY".
In my experience, they are single flush and do not normally back bud. (I had one back bud on 10 year old wood, but it died). They also are not predictable for me in activating needle buds. Sometimes it works, often enough to be cautious, it doesn't. But that is in my constellation of climate, culture and genetics of my stock.