I suspect so. That, and the struts themselves might not really be an OE equivalent in functionality, just one that the strut manufacturer makes that they consider to be close enough. More transparency by the manufacturers would be better. As in if they stated in their documents that it's dampening is softer/ the same / stiffer than the OE strut. That and things like for the OE they used different struts for different trim levels and the aftermarket uses the exact same strut for all trim levels, so you already know for a fact that something is going to be different. I'm specifically thinking of a Ford Escape (2013-2019) where the struts are different depending on the wheel size, but I'm sure there are a lot more examples like this.
On my particular vehicle (a 1999 Oldsmobile Alero) I will be replacing the bump stops because they are damaged. Probably the according rubber boot as well because they were made in 1998 and probably should be replaced. I don't know about the springs, they might be good and that is the type of thing I would expect an aftermarket maker to compromise on.
