Well let me just give a detailed explanation of this.
To destroy the Sun, you need to overcome its Gravitational Binding energy.
When you move an object, that object carries kinetic energy, which is found by the formula of KE = 0.5*M*V^2, when KE is kinetic energy in joules, M is mass in kg, and V is speed in meters per second. Moving an object very quickly will oftentimes produce more than enough energy to destroy said object.
Because of this, many planet busts that occur very quickly will have far higher results.
This planet bust happens so quickly that the results end up in High 5-A.
This wasn't even a full planet bust and it still yielded 5-A results. Moving large amounts of matter at high speeds will yield incredibly high results. In the case of MLP's calc, it wasn't even using normal KE, it was using Relativistic Kinetic Energy. According to Einstein, all matter will require a higher and higher amount of energy as it approaches the speed of light. Matter cannot physically move faster than light, so any FTL matter moving instance in fiction must be thrown out. That said, this wasn't FTL, it was relativistic.
Moving an object as large as the Sun at relativistic speed requires an absolutely insane amount of energy, one that far surpasses what would be needed to break it apart and negate its GBE. Does this explain what is happening here?