Unifoliate vs bifoliate bulbs?

[mascia]

Hi everyone,
I've been intrigued by this behaviour for a while, so I decided to ask the experts

I thought that bifoliate cattleyas produced one-leafed pseudobulbs when they were seedlings, but once they were mature, all the bulbs would have two leaves.

The thing is, that's not what really happens, right?

Examples from my own collection:

1. A Bc. Maikai Mayumi that I started from 3 back bulbs produced two tiny bifoliate bulbs, then a medium unifoliate bulb and now a huge bifoliate bulb again.

2. A big and established Blc. Bruno Bruno produced a unifoliate bulb. It is just as big as the bifoliate ones, and I can also see the buds forming inside the sheath.

So, is there a scientific explanation for this? I thought that maybe they would produce unifoliate bulbs when the orchid is stressed or set back, but from my experience, it seems to be totally random.

Thanks!