"...is that true?..." No. JC did his own tests using 'Blue Pill' loads. High pressure test ammo. He went up in 5,000 psi increments, from the standard Blue Pill load of 70,000 psi to 120,000 psi. At that pressure, the left locking lug cracked. The same rifle, with no repairs, went on to fire a further 5,000 rounds of service ammo with no further damage.
"...have used 220 grain Winchester Silver Tip bullet in my M1 rifle..." You too? The ammo I used, long ago, was factory. No fuss. No bother. Blew a ground hog into next week though. From very close range. Impressive bullet, to say the least.
Both Federal and Hornady load ammo specifically loaded for M1's. Don't know if it's available here. Haven't used any factory centre fire for eons.
"...rifle was designed to function with ANY standard U.S. military .30-06 ammunition..." The Rifle was designed to use and all testing was done with .30 M1 ammo with it's 174.5 grain BT bullet at 2640 fps. No such thing as .30 M2 until 1939. The .30 M1 ammo was found to have too much range for National Guard ranges. So they went to a lighter, flat based bullet at 2700 fps then upped the MV, in 1940, to 2800 fps to match the ballistics of the .30 AP's 168 grain bullet. This was the standard W.W. II issue ammo.