It's your thread...
I know Palmer wrote that and he's a reputable source... mostly. He also wrote that at least 9 years ago, probably longer. Most book revisions usually lack thoroughness and critical editing on existing matter. The consensus on the innuhnet nowadays seems to be that rolled, flaked, quick, and instant oats are all pre-gelatinized by the hot rolling process and can be added to the mash directly (I'd run them through the mill though). Only whole and steel cut oats need to be pre-cooked.
When specifically re-reading that section on adjuncts, Palmer doesn't mention cooking wheat, barley or any of the other flaked adjunct. So why would oats be an exception, except that they come in 6 "different forms," unlike the others. Look at flaked wheat, that looks pretty much the same as rolled or old fashioned oats, don't they?
I eat a lot of oats, raw, cooked with milk, and sometimes in cookies or bread. When cooking "old-fashioned" oats they cook and dissolve rather quickly, like within 5-10 minutes. The steel cut oats take much longer and stay a lot chewier even after 30 minutes of simmering.
Useful hint:
Oats do give a bit more flavor when toasting them in the oven a bit before adding to the mash. So you may want to consider doing that, depending on style.