As @cleeds stated, LPs aren't made in clean rooms and, in fact, some record pressing plants are very messy places.
Having worked in a clean room environment and having analyzed new LPs, I would say that most record pressing plants are dirty. I would definitely clean any new LP. Most new LPs have significant contamination on the surface which is not visible to the naked eye. Much of this contamination is due to mold-release compounds. Once cleaned in an ultrasonic cleaner your LPs should be fine for quite a while if handled carefully and stored properly.
Your cleaning process looks fine.
Having worked in a clean room environment and having analyzed new LPs, I would say that most record pressing plants are dirty. I would definitely clean any new LP. Most new LPs have significant contamination on the surface which is not visible to the naked eye. Much of this contamination is due to mold-release compounds. Once cleaned in an ultrasonic cleaner your LPs should be fine for quite a while if handled carefully and stored properly.
Your cleaning process looks fine.