What I hadn't appreciated from your original post is that there are two similar but actually different GearIT cable products, with different specifications, advertised by different sellers. It's not one cable product with one listing for two different voltages.
It seems that the 300V version is to use with a 120V supply, and the 600V version is to use with a 240V supply. So you would need 600V rated cable for your application.
The only comment I'd make is that a couple of reviews mention the price is high in relation to what is available from Home Depot and the like. It actually looks a robust cable with fine stranded oxygen free (it claims) copper, and I don't see any reason to doubt its suitability. It is tested and certified to UL standards by Intertek, who in my experience are a reliable organisation!
PS just below your Amazon link, you say COOW wire, but the link takes me in the UK to a page that says it is SOOW - but probably irrelevant