All relevant points. Especially point out the reality of private labeling products = separate brands backed by different marketing companies selling the exact same product in different packaging.
Many top-notch name brands within the health supplement industry were built using this protocol. This works great, if the product is 100%, but if the product is compromised by lack of quality control or worse, intentionally cutting quality to maximize profits, great errors and harm may result.
As far as UL goes, my experience was pretty impactful. Outside of that my experience, I am trusting that they have their own facility and quality control as you say, but in the end, I am trusting what I read on their website and what you and others share about your experiences.
In the end, If you dig hard enough on any company, you will find dirt. Few companies are squeaky clean. In the end, we all need to make the best decision we can for ourselves.
Sharing information and experiences helps everyone with their own personal decisions.