I wouldn't consider it a reversion per se - there is clear evidence of variegation on those leaves. Typically a reversion on a variegated JM is clearly a solid green and with often a different leaf size and shape. I'd consider the photo to be more illustrative of an example of juvenile foliage.

Wonderful, thank you, this is good to know. I have the tree in full shade on my covered patio, but have read conflicting info that they require lots of sun to be a whiter cloud color... or completely opposite: that they burn tremendously in full sun and shade is the best way to display them. If you have any experience with the ukigumo cultivar, I'd be curious to know your thoughts. Cheers :)