I'm not exactly sure what you are saying. I think you mean the product was labeled (1) as vegan and (2) being made with essential oils (not fragrance oils), right? I don't know of any watermelon essential oil, either. To get that smell, I believe you would have to use a fragrance oil. However, there are some companies that sell fragrance oil/essential oil blends. So, technically speaking, if the watermelon scent was created using one of these type fragrances, labeling it as an "essential oil blend" would be accurate (although misleading, IMO). I have used "Crafter's Choice" Chamomile Lavender Fragrance/Essential Oil Blend. It smells wonderful; but it is neither a true essential oil, nor a true fragrance oil. If I were to sell my products (which I do not) I would list it as "fragrance" on the label and leave it at that.
Silk would not be vegan. Any animal product, including honey and beeswax, wouldn't be. However, the "silkworms" aren't killed in the production of silk. (They're not even worms, they're caterpillars.) The silk is the cocoon the caterpillars (incorrectly called a worm) spins in order to pupate. Once the metamorphosis occurs, the moth emerges from the cocoon, mates, lays eggs and dies. Unfortunately, since the majority of silkworms are captive bred, the moths no longer fly away and live their (very short life span) in the wild. It is this cocoon that is boiled and turned into the silk we use for soap and cloth. A silk farmer would have to be daft to kill off their worms; they wouldn't have any subsequent generations to harvest. (I once toyed with the idea of raising silkworms. Then realized I don't have the time or patience for it. But the whole process still fascinates me, so some day I may re-visit my silk farming. Instead, I did vermicomposting. That didn't go over too well either. I starved my poor wormies!! One person just doesn't produce enough veggie matter to support vermicomposting.)
I think the problem with reviews in general are people are not actually reviewing the product. They are giving their opinion of the way it looks or smells or if it matches the color of their eyes, etc. I've seen reviews of products that went something like: "This stinks! I'll never buy from this company again. They won't even give me a refund for this garbage." OK. That's not a review of a product. That's one person's (negative) opinion of a fragrance. I think. I don't remember what they were "reviewing."
A review of the product would be how it works. Does it work as described? Does it look as described (correct weight, color, etc). If it is soap, does it lather? Does it get you clean? Does it take the hide off of you? Does it leave you feeling dry? Does it rinse well? Addressing issues such as labeling after purchasing a product is not part of a product review. I believe that is something that should be addressed privately with the seller. If the web site (or where ever you purchased the product) had the ingredients listed then you knew you were purchasing a watermelon scented vegan product made with an essential oil blend and silk. If you had any doubts or issues with the ingredients those should have been addressed with the seller before the purchase was made. However, if the product was not correctly identified prior to purchase, then IMO, you have a legitimate issue to present to the seller and can request a refund. And I think it would be perfectly within your right as a consumer to include that information in your review of the product to warn others that may be planning to purchase the product expecting it to be vegan and contain only essential oils.
I don't know of any rules, real or not, not being critical of other soapers. I know on this forum, and in life in general, it is considered quite rude to bash someone for their practices especially if they are unable to defend themselves. As a consumer, you can leave a review of any product you would like. You can do that here, too. Just make sure if you are critical or negative, you can take the heat when it turns on you. I'm not one to mince words. I tend to be blunt and to the point. Which gets me into trouble. A LOT. However, I appreciate it when people are honest and straightforward with me. I firmly believe in: "Don't tell me what you think I want to hear. Tell me the truth." The signature line on my email at work is: "I always tell the truth. Sometimes, the truth hurts worse than a frying pan to the face."
I hope this helped you a little bit. If not, that figures. I'm just babbling on again...