As pmOS folks (and anyone running alpine on their desktop or server) will happily tell you, size reduction is not a goal only relevant to container runtimes.
"Alpine Linux was chosen as the base distribution due to its low storage requirements, making it more suitable for older devices. Excluding the kernel, a base installation takes up approximately 6 MB"
i guess that would also make a more secure phone, one that is less likely to call it's mother ship.