Sublime is a native C++ app. It uses a minimal custom framework built on top of I think skia which actually mediates the drawing on hardware devices (or the CPU). As described by the articles the power usage comes from causing the hardware to repeatedly exit a low wattage deep idle state to update the UI not to do with the amount of work required to render the update.

This is actually more noticeable for efficient apps than inefficient/bloated apps as the latter don't get as many chances to enter deep idle states in the first place.