Connecting Amazon Seller Account to your Seller Assistant account gives you a lot of advantages. Doing so you can:
use Bulk Restriction Checker feature
see personalised information about the product: restrictions on the sales of the specific product (feature "Brand Gate")
get the data about the product directly from Amazon servers
avoid some errors from appearing e.g. Offers Parse Error, Fees Parse Error, Product Parse Error etc.
Connected Amazon Seller account also speeds up loading of the extension on product pages.