Whether or not the misuse of the word hybrid drives you nuts, what you are doing here is helping to perpetuate the confusion. A hybrid is a plant that is the result of crossing two
different parent plants. Once that hybrid self pollenates and produces offspring, further generations cease to be hybrids. (f1 = hybrid, f2 and on = not hybrid)
Technically a cross and a hybrid are kind of the same - the product of pollenating one plant with a different one. But there are subtle differences. A plant breeder will cross breed different parent plants to end up with stable gene stock plants that will be parents of a desired hybrid seed. In the case of the Cajun Belle, for example, many generations of plant selection resulted in two stable parent plants that show a desired phenotype. When these two parent plants are crossed, the desired hybrid Cajun Belle seed results. Same seed of known qualities every time. This gives us two things - desired qualities like pod flavor/shape, plant habit, disease resistance; and it gives hybrid vigor. Both are selling points for hybrid seed.
A cross is just that, two different plants cross breeding. The result is an f1 generation like a hybrid,
but a hybrid is a cross of two specific parents who were developed and stabilized with the sole intent of producing that one specific hybrid seed. All hybrids are crosses, but not all crosses should be called hybrids.
If you self pollenate a Cajun Belle, it's offspring cannot be considered a hybrid or a cross any longer. Their parents are the same plant. These are called f2 plants. If you keep doing this, generation after generation, you will eventually stabilize it. But if you allow it to open pollenate and it happens to be pollenated by a different plant, then you start over with another f1 cross.
Also, open pollination does not equal heirloom. You can pollenate an heirloom plant in isolation and still call it an heirloom plant. You could also allow it to pollenate openly and still call it an heirloom, if it maintains genetic purity by self pollenating. Some heirlooms are the product of plant breeding (deliberate cross breeding and selection) to end up with a desired plant. While others may be the product of many generations of cross breeding that resulted from open pollination, where the grower selects for desired traits that are the result of years of natural selection of traits.
There. Now my brain hurts and it's too early to dull the pain with beer.