Only the Stone Remains

["Rika and Kevin" <kevrik@shaka.com>]

Okay, so we have this stone that says William de Saint Clair , Knight Templar. The consensus is that this is the tombstone of the William who died in Spain in 1330.
I have no Templar point to point, thrust or parry; but this is intriguing to say the least. The first question, is it genuine? It would be a most bizarre and unusual forgery.
Second question, who authorized it? I would imagine the family, which brings up #3;
Why that inscription? I would imagine it was easier than chiseling " died in Andalusia, Spain while attempting to bring the heart of Robert Bruce to the Holy Land". 
Why not "Lord of Roslin" ?
He also seems to have been a relatively young man, not old enough to have been a Templar before their demise.
Any thoughts ?
Take care, Kevin