There are lots of factors that go into deciding the weight limits on bicycles, as well as the actual weight of the rider. All bikes will carry a much higher load than they say, as a ‘factor of safety’, to cover stuff like impacts, pot holes and fatigue life of the frame.
For example a 80kg rider who rides hard on rough roads, jumps kerbs etc. Is probably going to ‘stress’ the frame and use up more ‘fatigue cycles’ than a 110 kg who is more gentle , on smooth roads .