I have no experience taking those cuttings, but I love these trees (the thorny variety) and have read over and over again that older trees do not produce thorns above about 15-ish feet, and they do not tend to grow thorns when grown from cuttings above this height. That said, the seed from those trees should produce thorny trees (except for about 10% of them that are naturally thornless.) And, I have heard that the suckers will too.

Plenty of places seem to be selling inermis seed (including treeseeds.com.) Gleditsias grow very quickly (6 or 7 inches in just a few weeks from seed). And the suckers from those seeds should not produce thorns.

Just to give an idea of how quickly they grow, this pic is of seedlings I started about 3 weeks ago. The pots are 6" for reference.

If they are like citrus, then yes they will result in thornless plant.