That airplane was converted by moving the main gear forward, the gear is not long enough to raise the attitude to the stalled attitude on the ground....
..therefore it is not possible to three point it in the full stalled attitude....so wheel landings will give you better results.
The people who did that STC changed to the higher gear just prior to their not offering the STC...as far as I know the STC is no longer available for new conversions.
Go back and look at the nose attitude on the one I converted versus that one and it is self explanatory why there is a difference when attempting to three point them.