No idea why this is being downvoted. This matches what I heard about Plasma's mobile endeavors.

In 2012, at the Akademy (KDE conference) in Tallinn, I spoke with Plasma developers who were, at the time, working on a tablet called "Vivaldi", which was supposed to ship with Plasma Active (the KDE 4 version of Plasma Mobile) based on Mer (the community fork of Meego). And they really struggled with the hardware part: They carefully assembled a BOM of parts for which open-source drivers were available, ordered test devices, built the whole software stack. And when they were ready to start mass production, the manufacturer was like: "What, that chip? That's soooo last month. We have this new chip here, which is completely undocumented, but we have an Android driver for you." Last I heard, they never got an actual device shipped because of that mess.

I don't know if it's gotten any better since then, but I can easily imagine how that situation led them to base the new Plasma Mobile on the Android HAL.