“Similar but not identical and not parallel.”
Amazing. You can’t see (or I should say refuse to see) the obvious, that Matthew and Luke are about the exact same event. And yet when it comes to the phrase “this generation” in both of the chapters, you change the “this generation” in Matthew to mean “that generation” but keep the “this generation” in Luke as is.
Look up the meanings of the words "similar" and "identical" in the Books of Oxford or Webster. Like those two passages, the meanings of those words are "similar" but not "identical".