According to related literature, the physiological differentiation period of apple flower buds is in mid-June, so trunk girdling should be carried out from late May to early June to promote flower bud differentiation. The effect of girdling the red Fuji apple tree in early July on promoting flower bud differentiation will be obviously reduced (but it will promote axillary bud differentiation).
But you can do experiments around a few trees and mark them to see what the effect is.