Patches should always be lubricated with something before they are shot.
I know that more than one dry patch has become stuck in the barrel while it and the ball were being rammed down the bore during loading.
(If this happens, dump a little water down the bore and let it sit for a few minutes. Then dump the water out of the bore and ram the ball the rest of the way down to the powder load.)
The patches job is to seal the rifling and to grab it tightly so that when the gun is fired it will transmit the rotation to the ball.
Because sealing is a large part of its job, it should always be thicker than the depth of the rifling grooves.
The lube on the patch not only helps with loading but it helps prevent the hot gases from the exploding powder from burning the material.
It also lubricates the bore and rifling so it is less likely to be torn on its way out of the barrel.
Folks have used everything from spit to vegetable oil to the store bought wonder lubes and they all work, some better than others.
As a general rule, don't use a petroleum oil on your patches. The oil will mix with the fouling produced by the black powder (and other powders) to produce a hard tar like fouling that is much more difficult to remove.
Where black powder fouling is water soluble, petroleum oil fouling is not.
As for pre lubed patches often bought at a gun store they are fine If they are NEW or fairly new.
The problem here is that many of them have been sitting on the stores shelf for years and the oils/lubes that are on them will cause the material to loose its strength and tear when they are loaded or shot.
While I'm on the patch subject, when a muzzleloader is fired with a patched ball, make an effort to recover the fired patches.
They should not have rips or tares in them where the ball contacted the bore.
The center area can look almost new to dark brown or even slightly charred but it should not be burned thru.
The outside edges will always look frayed. This is normal.