You can't make a threaded hole in carbon fiber at all; it's impossible. This isn't the issue.
The issue (according to the YouTube experts) is that for mass-market bikes, the manufacturers have somewhat poor quality control and manufacturing tolerances (as far as drilling holes apparently). For a press-fit BB (bottom bracket), you need an extremely round hole, accurately sized for the BB to press into (hence the name).
For a threaded BB, this isn't an issue, because those aren't pressed in. Those have an aluminum threaded part that's bonded into the hole; the hole doesn't have to be super accurate, just good enough for the aluminum part to fit into properly and get glued in. The aluminum part has the threads and perfectly fits the BB, and since it's machined out of aluminum at some other factory, doesn't have the problems with tolerances that the CF parts have apparently.
The issue (according to the YouTube experts) is that for mass-market bikes, the manufacturers have somewhat poor quality control and manufacturing tolerances (as far as drilling holes apparently). For a press-fit BB (bottom bracket), you need an extremely round hole, accurately sized for the BB to press into (hence the name).
For a threaded BB, this isn't an issue, because those aren't pressed in. Those have an aluminum threaded part that's bonded into the hole; the hole doesn't have to be super accurate, just good enough for the aluminum part to fit into properly and get glued in. The aluminum part has the threads and perfectly fits the BB, and since it's machined out of aluminum at some other factory, doesn't have the problems with tolerances that the CF parts have apparently.