Gabe15

The plants beyond tetraploid (tetraploids are fine, just like pentaploids, hexaploids...those don't work) are the results of dead ends in breeding programs, they are obviously not a good choice plant to breed with so they don't make it anywhere.

As for seeds in edible bananas, this is not as weird as it sounds. The reasons for sterility are complex and vary between individual varieties. The more "advanced" cultivars have been chosen to be completely sterile, this means they cannot receive or produce pollen essentially. However, before there were advanced cultivars, they could all form seeds and there are still many of these around. The reason you don't see seeds in Cavendish bananas is because they cannot be fertilized and even if they could there is no pollen being produced anywhere. Some edible varieties can receive pollen, but if there is not a pollen source they will not form seeds, but sometimes wild plants or other varieties that do produce fertile pollen could be nearby and so you may find a few seeds in those varieties capable of forming them.

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Growing bananas in Colorado, Washington, Hawaii since 2004. Commercial banana farmer, 200+ varieties.