That’s right. Speaking as someone who teaches writing one-on-one…it’s damn hard to write well, and a lot of brilliant STEM kids can’t do it. To me, writing is a lot easier than engineering, but that is clearly not true for most engineers.
That may well be true, but for a bunch of external reasons, they are usually not requiring a lot of writing of their students or giving intensive feedback on whatever writing there is. I don’t know whether people who teach first-year writing and first-year math at Yale would agree with each other about whose kids are better prepared.