The instructor (Bishop Janet) was VERY careful to not mention ANY company by name, but to say one must test any product they buy for accuracy. And she did not recommend any company either. Jim did say there is a recommended list of vendors on the site.
It was people in the class that were complaining about their bad experiences with specific companies - most notably Ocean's Lab which people said they were having problems with getting orders in a timely way and someone said their product was a weak concentration. I know people personally who have had problems with Ocean's Lab lately. I can not speak to any other vendor.
Janet was clear that if a product was not the correct concentration that she would not recommend ingesting it, and the consumer should test whatever they buy.
I was told that any weaker stuff can be used for external purposes - like foot baths. I even spray my sponges, and around the kitchen and bathrooms, etc. with it, and a precise concentration is less important for something like that than it is for when you take it into the body.