Apple and Qualcomm don't sublicense so they are not really Arm competitors. Plus, ARM was always a convenient way to mutualise development costs without the risk of collusion. I am not sure it's changing.

Apple and Qualcomm absolutely are Arm competitors. Otherwise, Arm wouldn't have sued Qualcomm over the Nuvia deal.

Arm makes far more money licensing their cores than their ISAs. If their entire business was reduced to just licensing their ISAs because their cores can't compete against their customers' custom cores, then they will be at a highly disadvantaged position.