Two flowers are somewhat common, this is the first time I've seen three. Improving on the norm would not disqualify them, judging is all about rewarding improvements in size, color, and floriferousness.
I guess I question what the norm should be.
Burhard most likely improved the trait through selection and breeding within pool. However, hypothetically, let's say he was able to achieve the same results by crossing outside delantii, then backcrossed n generations while selecting for form and 3 flowers-trait, would anyone know the difference? The results are the same: improvements in size, color, etc.
I'm not a big fan of this double standard and would suggest that the current system encourages people to be dishonest about the breeding background to get rewards.
Again, not suggesting anything fishy about the example here, those are amazing plants (and my guess the 3 flower-trait is more attributed to the general health of the plant and excellent horticultural skills than simple gene inheritance). Just speaking more philosophically about species and line improvements as a whole.