> If it were simultaneous in both frames, then what exactly
> would the "relativity of simultaneity" be?  (I can't wait
> for this one).

Rod: The flashes hit simultaneously in the track frame at t=x,
and simultaneously in the train frame at t=y.
These are relative times.

c+v and c-v are applicable in the track and train frames
wrt to the other frame but not to each owns frame.
Otherwise, that would mean that the speed of light is not
c in every frame.
Do you now understand what Ken is trying to teach you?

Rod Ryker...
It is reasoning and faith that bind truth.