I think the largest corporate R&D lab at the moment must be Huawei. Last time I've heard from someone working there, they have more than 10K PhDs working for them and even only half of them working on R&D that is really massive. It also being helped by the fact its founder is an ex military R&D engineer.
The silver lining is that since doing R&D is necessary for progress and innovation, it will happen elsewhere. I foresee that the majority of R&D exercises will move to university and industry sponsored research will be the norm rather than the anomaly. This is also fueled by the fact that graduate students' stipends are much much lower. You did mention that in Bay Area the researchers are paid half of the FAANG senior engineers. In most developed countries, the salary of university graduate students probably a quarter (4x lower) of the company's researchers. The developing countries has the worst by being paid 10x lower than the BAY Area researchers.
Google has a ton of PhDs, too, but the vast majority don't do R&D. I'm guessing the same is true at Huawei.
Anecdata: My team of 12 or so at Google had (I think) 4 PhDs, and what we did was the usual "turn one proto into another" Google work that barely required a CS undergrad degree, to say nothing of a PhD. My wife has a PhD, works as a software engineer, and also does pretty routine data plumbing work.
The silver lining is that since doing R&D is necessary for progress and innovation, it will happen elsewhere. I foresee that the majority of R&D exercises will move to university and industry sponsored research will be the norm rather than the anomaly. This is also fueled by the fact that graduate students' stipends are much much lower. You did mention that in Bay Area the researchers are paid half of the FAANG senior engineers. In most developed countries, the salary of university graduate students probably a quarter (4x lower) of the company's researchers. The developing countries has the worst by being paid 10x lower than the BAY Area researchers.