Could it be that heating issues are also because of the choice of their UI toolkit?

It looked like they're writing their apps in gtk, using the CPU for any animation and rendering - as opposed to some OpenGL solution that would do this much more efficiently on the GPU..

For reference, Rendering a simple, animated bar chart using QtQuick canvas, at 720p@60fps maxed out our iMX6 cpus - while doing the same on the GPU took like 30% cpu and the result was much more smooth.