At my company, we had difficulty making our landing pages rank when they were just written in React. We ran an experiment where we took out the interactive part

At my company, we had difficulty making our landing pages rank when they were just written in React. We ran an experiment where we took out the interactive parts of it and just put the static content into a html page-- and it performed better. The other engineers and I were flabbergasted ("it's not supposed to make a difference!") but our SEO expert was not surprised that there was inconsistencies in the Googlebot documentation, and it goes to show that we still don't have a lot of transparency into the google algorithms. I suspect that, like you say, it was a speed-to-paint thing. But when you're in a crowded keyword space it makes a difference. (As oppose to when you're just trying to rank for your own unique name--- looking at you, Preact ;) )