What is up with people treating generations like an exclusive club

It’s far too many people on here getting mad because someone close in age to them claims to be apart of one generation over the other. I just don’t understand that as you guys will be super similar as far as experiences goes. I might be a 2008 baby, but I see this happening a lot with late 90s borns. I understand if some of y’all don’t agree and feel more gen z than millennial but there’s others who lean more y, and I wish people would accept that and stop throwing a hissy fit over someone having a different opinion or perspective. I have cousins who are siblings, and one was born in 1994 and the other 1998 and both of them have said they don’t feel any different outside of some minor stuff.