Yeah but doesn't the NEMA 10-30 dryer plug have two 110V lives and one ground/earth. So changing to a NEMA L6-30P the only real hard bit is making sure that you wire up the ground/earth receptacle correctly. While the other two 110V leaves don't really matter which receptacle that they're wired to.
Not quite. The NEMA 10-30 outlet has two 110V lives and one neutral. The NEMA 6-30 wants two lives and a ground. Your your picture of the 10-30 incorrectly claims the neutral is a ground.