The chances of the alignment being coincidental is remote in the extreme. The sun does not rise close to the stone, but directly behind it (first flash) at the moment of the true equinox. As you are not a spokesperson for other archeaoastronomers you are in no position to assess what their opinions may be. Thousands of other examples eh? Hmm.
This is either one of two things. The deliberate positioning of a stone to mark the equinoxes, or an accident. Nothing you have said has convinced me its the latter. I have tried to answer your questions as clealy as I can, and welcome the opinions of others. I'll bow out of the conversation now as its going round in circles. We'll leave it for others to decide eh?