I definitely understand your concern. I can say from my experience that I have not observed any negative side-effects yet (four bags in) with a varied, but Huel heavy diet. I have given what information I have below, but unfortunately, you will probably need to decide on the answer to the question for yourself.
I am not a lawyer, but based on my understanding of consumer protection laws, there is only going to me a “massive recall” in the event that Huel is either fraudulently stating what is in their product or there is a contamination issue with the product or one of its ingredients. Both are risks that are not specific to Huel, and the general public generally cannot identify these issues.
If the question is whether, from a nutritive/biological standpoint, a 100% pure Huel diet will provide all dietary needs and be free from complications; the true answer is probably we don’t know. Huel has a page about nutritional information that I would encourage you to read. The issue is that the human body’s functioning is enormously complex and not entirely understood. To the best of the currently available knowledge, Huel looks like it should be complete and meets or exceeds the government’s dietary regulation. Whether something new will be learned in the future that shows a deficiency (or problematic excess) only time will tell, though this would also apply to to other food products and diets (is Atkins safe, etc.))