Yeah a really big and fundamental difference between an Android phone and an ARM laptop is that a phone has to have a low level radio stuff that have to be close sourced and fully locked down for regulatory compliance in most countries, so that they transmit radio stuff within legal bands and within legal transmission power and all that, you simply cannot open source those or even keep them user-accesable and mod-able without your device being illegal to be commercially sold as a mobile phone, because then anyone could mod them to operate as radio equipment outside the legal range. And that requires the firmware of those radio stuff to be provided by the manufecturers of those radio chips and devices (not the OEM of the phone).

In fact the inherent complexity and overhead from this was one of the biggest hurdle for early smartphone manufecturers and smartphone OS developers like Nokia and their Symbian OS to become successful. And figuring out how to deal with this efficiently between all of the radio stuff suppliers and smartphone OEMs, was one of the major reasons iPhone and Google's Android were able to succeed commercially in the last decade. In Android this is one of the things that necessitated the HAL or hardware abstraction layer, so that the standardized Android system components and especially Android kernel don't have to directly deal with more than thousands of different models of radio hardware from all kinds of different manufecturers that all require different drivers and such because of how they are close sourced and locked down, whereas on a regular Linux distro running on a normal ARM laptop, the drivers of all those devices can be included into the kernel and redistributed because they are open source.