Opinions on Brandon Sanderson's take on writing speed and how it relates to story quality?

Apparently he responded to a few fan opinions and theories regarding Stormlight Book #5, but what really caught my eye was his take on writing speed and completing projects on a condensed timeline:

"Take more time" is great in theory, but if it starts regularly taking four years between Stormlight books as it did between the last two, that can easily become five, which can spiral out of control. Suddenly, I'm 80 before I even START the final era. So I really feel I need to work it with three years between, which means I need to do Stormlight books in 18 months or so, in order to have time between them to recharge.

Fortunatley, for most highly-creative endeavors, more time doesn't always equate to quality increases. In fact, it often has a negative effect on the writing, counter to what people expect. This makes sense if you think of other professions. You wouldn't expect an artist to improve if they painted less, or an athlete to perform better if they took more time off. Of course, you need to avoid burnout, but keep in mind that the intense, furious, act of creation sustained on a project is exhausting precisely BECAUSE of the benefits. Your entire mind and subconscious become devoted to fixing the problems in the narrative, to making connections between plot lines, to improving the flow of the storylines. This is hard for Stormlight because the books are so long, but also because of the mental load of doing this across so many plots, themes, and character arcs.

I'm a slow writer working on increasing my speed, and I have to say I have noticed a bit of some of what he mentions here when I'm able to fully devote myself to getting words on the page.

But this is probably my first time seeing a successful author suggest that being able to work intensely on a project on a condensed timeline might straight up better in some regards. Usually I mostly hear authors say they do this because they have to for deadlines, not that they think it also helps quality.

And yet, I can't help but look back at how fast George R.R. Martin got those first 3 Game of Thrones books out. He had all the time in the world for the first one, fair enough, but the next 2 came out in 2 years and are extremely well-regarded. Even he looked back at how fast he was writing back then compared to now (lol) and said something like "I have no idea how I managed that."

Would love to hear from both slow and fast writers (and particularly from people who are both) about what they think when it comes balancing speed and quality.