“Turn data into images” is a much better phrase than “rendering.” Anyone who is not intentionally being pedantic for dramatic effect would understand the purpose of the product based on reading that phrase, whereas “Datashader: a renderer” is less clear and could refer to products with an entirely different scope/purpose.

Their product page is well-written and accurate. It sounds like you want them to purposely describe their product as something that is inferior to what it actually is.