This is the answer.

The more insidious bit?

Most manufacturers don’t actually know what’s in the masking fragrance, because they buy it from a third party who has no legal requirement to list the ingredients.

So even “unscented” products have this stuff in them that’s a mixture of perfume and preservative, the contents of which are a trade secret. There’s very few soap, deodorant and aftershave suppliers who actually know all the chemical contents of their products, and even fewer who are willing to share that information with the customer.