Vendors of Nebuka bunching onions always show a photo of bunching onions with bulbs that are much larger than the normal slim bunching onions bulbs. Has anyone grown Nebuka and produced these larger than normal bulbs...or is this just a wishful thinking type of advertising?

I've never grown that variety, but looking at the pictures, they look smaller than bulbs I've gotten from Crimson Forest. So, I'm inclined to believe it.

Here's an eBay link that has the photo I'm referring to. Is your Crimson Forest bulb larger still?
https://www.ebay.com/itm/175203874268?var=474735368986