Sailing to windward in 10 - 15 knots, I noticed the leech of my main is severely 'scalloped' (for want of a more technical word).

I didn't get a chance to photograph it and have looked far and wide for an image on the Net to illustrate it.

The attached photo loosely (between 2nd and 3rd batten mostly) resembles the scalloping, however, it is far more pronounced on my sail.

My main has full-length battens and is loose-footed. Rig is fractional, no runners.

Any thoughts?

(Image Credit: Joe Cooper Hood Sails)

maybe if the scalloping is just above a reef ,it may be stretched .

Could it be possible that the battens are too long as it is along the leech between each batten this scalloping occurs?

No, very tight.

The scalloping is intentional. It reduces the sail area slightly but prevents or reduces leech flutter

All the above is possible, however the following might cause it.
Usually, there is an adjustable line running inside the main's leach and foot to adjust the leach and foot tension, stop the leach and or foot of the sail fluttering.
In many instances this out of sight out of mind line is forgotten. On many cheaply made sails it is tied down to an eyelet or velcroed under a pocket never to be opened again. Better made sails use a jam-cleat to make adjustments a breeze.
The sail ages, years go by and the material stretches while the leach and foot line - made of spectra - does not.
Also, after tightening the leach line in higher winds many forgets to loosen the line when the wind drops causing the leach scallop or scoop the sail looking like Mother Hubbard's washing in the wind.