Just because it works really well doesn't mean it has PGRs in it. If you recall, it was Advanced Nutrients themselves that blew the whistle on many other companies that were adding PGRs to their products and not telling anyone.
It's irresponsible to try to start rumors like that based on a fundamental misunderstanding of plant nutrition. "Your kelp" doesn't mean anything useful. What is "your kelp"? How does it compare to "AN's kelp"? And what else does Advanced Nutrients put in Bud Blood in addition to kelp extract? We don't have to jump to the conclusion that if we don't know what it is then it must be bad. That's only required if we've decided - without any real knowledge - that we want to believe it's some dark scary secret.
Remember, we attribute qualities in others that we possess ourselves. Someone who would never tell a lie doesn't see a world full of liars. We all assume motives in others reflect the motives within ourselves. So distrust of others indicates distrust of ourselves.
The truth is there are many industry secrets. No one wants to tell the competition exactly how to do what they do, because that makes it harder to make the better product. To make matter's worse, politicians and other government morons decide what is and isn't a plant nutrient. Not scientists. Not people who actually know what they're talking about. No, in order for the ingredient you use to make plants healthier to be legally printed on the label as a plant nutrient, you've got to prove in a way that can convince a politician (who lies for a living and thus assumes everyone else lies for a living) that it really does help plants. That costs a lot of money in scientific testing. The only company I know of that even runs its own lab on any real scale is Advanced Nutrients. Who pays for the testing? Not the company. Businesses don't pay for ANYTHING. It all gets factored into the price of the product.
So, would you rather all the nutrient companies do this exhausting testing so Perfectly Harmless Plant Additive #007 can get put on the label of a bottle that now costs 20% more, or would you rather they just put it in there as an unadvertised "stabilizer" or some-such that the government doesn't care about as long as they don't publicly claim that ingredient makes plants healthier?