A large number of Apple devices in the field, and even still for sale by Apple, have AMD GPUs. It's most likely legacy support driving its inclusion -- if Apple abstracted the pluggable device, appropriately branching it for their existing AMD and new chips seems a given.
It's extremely doubtful any new Apple Silicon device will come out with AMD GPUs.
It's extremely doubtful any new Apple Silicon device will come out with AMD GPUs.