It does "run", but it's not really running Linux. It's just android with a halium layer running Linux software on top. So when android support ends, which it will seeing how they've not been great at software support, your "Linux" build will also no longer get updates. That's why Mainline Linux is such a big deal, as even if support ends, you'll still be able to get the latest Linux kernel and distributions can continue basically forever supporting the device.