I've no doubt your quote is good; I've seen similar. But my point was, he was quoted as having changed his mind privately by 1870, when he unbosomed himself of his private thoughts to a visiting ex-Confederate from Texas. That man confided in a minister and seminary dean he knew, who in turn published the recollection in his memoirs, near the end of the century.
The confidential conversation with Lee took place at the close of a meeting called by the U.S. Army of the surviving senior Confederate generals. General Rosecrans presided, and was charged with reporting back what the Confederate generals were thinking. This was at the time the Force Acts were under active consideration.
Interesting to ponder if something had spurred Lee to change his mind in April of 65 instead of 70. If he had given the order to head for the hills and begin “irregular operations,” who knows what the USA would look like today? A GW could have stretched on for a decade or longer. The North might well have quit first. Interesting alt history.