WPA rules say, "If the cue stick contacts the cue ball more than once on a shot, the shot is a foul." It does not constrain that to just the tip hitting the ball more than once. If you contact the cueball with your tip and then separation and then contact the cueball with your ferrule (all in one continuous stroke), that's still a double hit.
Now lets say the tip hits the ball and the ball slides off the tip into the ferrule with no separation at any point all in one continuous stroke. You might argue it was not a double hit because there was no separation / secondary contact. But that also matches the definition of a touched ball which says "It is a foul to touch, move or change the path of the cueball except when it is in hand or by normal tip-to-ball forward stroke contact of a shot." In this case the path of the cueball is altered by abnormal ferrule-to-ball sideways steering. There are intentional miscue trick shots / proposition shots famous for this technique.
The miscue rule in the WPA rules only exist to be lenient on the player making an accident. It's not consistent with the logic employed in the double hit, touched ball, and push shot rules. In fact it acknowledges that some miscues are double hits. It knows it's being inconsistent with the logic. It intentionally marks itself as an exception. You can appeal to leniency to the player or you can appeal to tradition for its existence. But appealing to consistency with the logic of the other rules as a whole doesn't really stand up.
The scenarios that stand out to me is like when playing 8-ball. Your opponent is stripes. They're shooting at the 10-ball that's an easy hanger. They're putting right spin on the ball to play position using the rail after contact. They accidentally miscue and we all hear a loud *tink*. Instead of going straight the cueball squirts off at an unnatural 45 degree angle and catches the 12-ball instead, finds a rail, and happens to get a full snooker from all the solids on the table. As the rules stand today, they got lucky. The rules don't have to change. But if they did change, I would be an advocate for that shooter to have fouled and his opponent gets ball in hand.