There's nothing much special about phone silicon. They generally run a bit slower than their desktop/laptop counterparts because of power and heat limitations.

At the top end on a desktop power usage doubles for lower double-digit percentage gains. You can shave that off and not lose much. Laptops are a lot closer to phones than they are to desktops when it comes to power and thermal limitations*, so re-using a "phone" chip really isn't crazy.

* 100W power usage on a laptop is entering silly territory, but on a desktop that's the bottom of entry-level rigs.

> Laptops are a lot closer to phones than they are to desktops

Introducing the MacBook Neo.

And here I am with a laptop with a 450W brick next to it to make it function…

There is and there isn't. Your phone, almost certainly, with a shorter list of exceptions than not, has a locked bootloader and consequently cannot run unsigned software with full permissions without additional work. Sometimes that work is impossible to do. In terms of capabilities, sure, your phone is as capable, if not more capable than a desktop computer from a decade or two ago. The phone in my hand that I'm writing this from is 100 times more powerful than the computer I had as a kid. So that's an important point to make. However the specialness of phone silicon is the locked down bootloader and the downstream effects of that. You can point out exceptions where you can unlock the bootloader, but those are exceptions. The vast majority of phones you aren't going to get root on. So in that dimension, that's what's special about phone silicon. The signed chain-of-trust that is baked in and prevents you from running unsigned binaries with full permissions on phone silicon.