This claim is a bit surprising to me. I was under the impression Skia is an immediate mode renderer which ends up issuing a lot GL calls that could be avoided with a retained mode renderer.
That said a "lot of GL calls" for a 2D UI is actually a trivially insignificant number of GL calls to the actual GPU/driver for most cases. That's basically never the bottleneck unless you've done something insanely wrong.
For example: https://images.anandtech.com/graphs/graph11223/86100.png
Granted that's a 1060 but since we're looking at driver CPU overhead that shouldn't matter much. So 2.3 million draw calls per second in DX11 single threaded.
It's not until you start getting into the 10k+ draw calls a frame that you are putting your 60fps at risk.
It's often worth the work to avoid this anyway, after all faster is better if you're an engine/renderer, but it takes a lot for it to be an actual _problem_