No, the plugin isn’t GPU hungry, this is a bug with VST and its OpenGL implementation.
This issue has been there for ages, and it also happens on Windows. In fact when you open such plugins, it isn’t the GPU usage that increases, as it will only be a few percents, but the CPU usage however, will greatly increase.
OpenGL is supposed to relax the CPU but it does the complete opposite.
This behavior is present with hundreds of plugins from dozens of manufacturers, so we simply cannot say the culprit is the plugin vendor.
By analogy, every plugin manufacturer use the same code, which is called VST, and who develops VST ?
See :