They're just short handed ways of discussing odd behaviour.
Sometimes you just don't gel with a group/person. If you are an uber polite, people pleaser then you are always going to be surprised/hurt by the actions of those who are not.
Sometimes it hurts. Sometimes it happens so much it can ostracize you from a group because you have overthought it or don't have the brass neck to just breeze back in.
If you can just brush it off as the dynamics of friendship then you are one of those people who aren't caught on the hop and occasionally floored by the changes. Good for you.
But to casually dismiss those who are more frail socially as being the problem is not nice.... maybe you Wendy people without realising. I am sure most Wendy's don't.