Should the grower prune flowers to prevent fruit bearing in the first 3 years to help conserve energy of the young tree?

I doubt there is any need to do so. From what I've seen, the tree either doesn't produce flowers or succumbs to early fruit drop if it's not ready. The only time I've heard picking off flowers to be useful is for blueberries.

In fact, I'm going to Yu no shima (湯の島) in Gero, Gifu this time. Have you been?

I've never stopped in Gifu. I've heard it's nice, though.

Have you had a chance to use it?

I've never used that one, I always traveled on the Jouetsu Shinkansen.