I wonder if that is what opened for me today. It is a white double and is about the 30" height...really amazing! I had it labeled "Ludwigs Dazzler" but think that is a single. MY Blossom Peacock was only a few inches tall but it was bought late in the season at the grocery store. THe white one flowering is a 2nd or 3rd season one. IF it bloomed before for me it was short and less then spectacular. The height alone makes this one spectacular! (Both yours and mine).

Well... many say that the second and third blooms are better than the first, so perhaps this bulb likes where it's planted and is settling in! It sure looks tall and stately!

I think, it is related to root development.

That could very well be... mine are all grown in pots, so I would say scape height has to do with genetics/variety. I do notice that lots of roots seem to sit very close to the surface of the soil.