Have you noticed that most low wing, high thrust-line aerobatic planes will tuck to the undercarriage during knife edge? Cap, Extra, UCD, Funtana,... I can't think of one that doesn't. The only exception that I've experienced is the Katana 40 profile, which tucks to the canopy during knife edge, but it's not really a low wing & high thrust-line.

When wing is low and thrust line is high, there is a natural tendency to pitch downward because the pull is above the resistance.

The Yak, on the other hand, has the least amount of KE coupling. It's mid thrust-line and almost mid-wing.