Hi pimpernel,
That’s different from what you stated in your earlier reply. You stated you were interested “whether there were other synthetic materials used to make the cover not disclosed in the tag”. Now it’s “whether there are potentially any harmful materials that I am not aware of”. I’ll be happy to answer your question in the spirt of inquiry (although I think I covered it well with the information I provided and linked to earlier) but I have to admit I’m a little dubious, as your “questions” seem to be taking the tone of unsubstantiated claims posed as queries with an agenda.
There is no standardization of “harmful”, just as something that is termed “toxic” is dose dependent. These would be your own personal definitions of whether something was “safe enough” for you personally and unfortunately there is little documented information that will allow consumers (or anyone for that matter) to answer that question in all cases. Natural materials like wool can cotton can be “harmful” in certain circumstances, and synthetic materials can be “safe”. It depends upon the dosage and application. Post #2 here also has more information and links that can help answer the question of “how safe is safe enough for me?” in more detail yet.
There are a wide range of materials that are called “natural” that also include a relatively small amount of synthetic materials or components. Even some “organic” mattresses can include a relatively small amount of synthetic chemicals or materials, as I mentioned in my previous reply with what is allowed even in GOTS standards.
No manufacturer includes every small detail about every layer and component in their mattresses and they would quickly go out of business if they did because they would spend all their time explaining information that is mostly meaningless and would end up confusing most of their customers who really wouldn’t have enough knowledge or experience to understand or “translate” the information that they were receiving and would often attach more importance to it than it really has.
For those customers that for personal reasons have very narrow or specific criteria that would be unimportant to most people who would purchase a specific mattress then it would make much more sense to ask these types of more specific questions on a more detailed phone conversation before making a purchase than to expect any manufacturer to include every small detail beyond what is even legally required and IMO a more detailed phone conversation is an important part of any online mattress purchase anyway.
It’s also somewhat ironic that in some cases manufacturers that try to be as transparent and honest as possible can often become a bigger target for criticism than manufacturers that don’t provide any meaningful information about their mattresses at all. As you know I am a huge advocate for transparency but there is a limit to the amount of information that a manufacturer either can or should include or that a consumer will fully understand or put into a meaningful context before it will do more harm than good.
I think I covered this question in my earlier reply about labeling requirements. I’m not aware of every single type of fiber or material used in the covering of this mattress, or any other mattress for that matter, as this level of detail isn’t provided nor required to be provided. Even on other types of fabrics in other industries where complete specifications are required by the FTC, anything less than 5% may be classified as “other materials”. If your desire is to have complete details about every single fiber or chemical, regardless of percentage, in a fabric, unfortunately you’re going to be disappointed with any clothing or textile you come across, as that level of detail to the nth degree isn’t mandated or required, nor reasonably possible to provide, and even if it was nor would the provision of such information be meaningful/understood by the vast majority of consumers, and a manufacturer wouldn’t be able to make a subjective determination of what one person might consider “harmful” versus another.
I answered this in my previous reply, and you stated you received a reply from SleepEZ on this as well, so I’m not sure why you’re asking this “question” again. Yes, repairs in latex layers are sometimes made by manufacturers.
The foam could have a defect or it could have been torn slightly in handling (latex tears quite easily). Those would be the most common reasons. Many manufacturers consider small tears up to 3" to be normal in latex. Every manufacturer is different, and I wouldn’t have a concern. But if you personally have a concern and think it will negatively impact your particular piece of latex that you say has a repair in it, I’m sure SleepEZ would replace that layer for you if requested. 
Phoenix