Deepens on the kind of wetsuit and what you are doing. For example in spearfishing we lined interiors (something covering the neoprene) or open cell (raw neoprene) An open cell 5mm suit is much warmer than a lined 5mm suit.
When I am diving in an open cell suit I don`t notice the cold, but I dont dive in the middle of winter. Surfing I use a lined suit as they are more durable and and you move a lot more surfing. I do surf in winter and it is cold as hell. Water temp and wetsuit thickness need to match as well a good fitting suit.
Your question is difficult to answer. It certainly can seem warmer but not always.