Neoprene is naturally stretchy, which is good. It means that an off the peg wetsuit will give a perfect skin tight fit for all but a few of us. It also means that the body can move, shoulders can paddle, legs can turn and surfing is easy and fluid.
Some things increase stretch, most importantly the quality of the neoprene.
Different neoprene stretches in different amounts. The best ‘super stretch’ fabrics will increase by at least 100% when stretched, a less expensive neoprene perhaps by only 50%.
This does make a difference to the feel of a wetsuit and how tiring paddling and surfing in it can be. Some manufacturers ensure their mid priced wetsuits offer both value and performance by placing this super stretch neoprene in the shoulders (where it’s most needed) and cheaper versions in the rest of the body.