This is not an odd way to make a kilt. Virtually all tartan is sold double width and most kilts are "one-offs". In other words, there would be no reason for a kiltmaker to buy 8 yards of double-width tartan unless he/she had to make two kilts. Virtually all the kilts I make have a hidden join in the back for that reason.

There are other ways of fixing a moth hole, and your kiltmaker may have rewoven the hole with threads pulled from the tartan. You can determine whether a pleat was removed by looking for a seam - if there is a seam where the pleat was removed, that's what was done. But honestly? That would require _a lot_ of reconstruction (removing all the canvas, stabilizer, and steeking in the back of the kilt), and they should have charge you a boat load for the alteration!!