"Are you saying that no fully ripe jackfruit should be crunchy ? Not sure I agree with that as I have had jaks that were definitely to the point of past ripeness that were still crunchy. For as sweet, rich and flavorful as some of the crunchy jaks I have had, if they were truly underripe, how would you say they change other than as you say the texture ?"
No i am not saying that. I'm saying that from my observations, and from photos i see that are posted, many people tend to cut and eat the jackfruit when they are way under ripe: full of sticky latex, very crunchy, but also not as sweet as when fully ripe, also a lot less sticky when fully ripe!