Because ours is a centrally-managed service shared in common among all our merchants, it's not possible to modify how it works for one seller without applying the same modification to all other sellers, aside from the user-specific settings provided in Seller Admin of course.
The "Go Back" behavior is intended to cover cases where the seller is unable to use our standard javascript-enhanced cart button codes (which would display the cart as a lightbox inside the seller's page) nor even retain the target= attribute of our non-JS button codes (which would open the cart in a popup window/tab), so in that case the button works like an ordinary link, taking the buyer away from the seller's page to our cart in the same window; since there's no way for our cart to determine what URL the buyer should be returned to, we can only provide a Go Back button that works like the browser's Back button, stepping back in their browser history.
You may want to consider using our box.js cart script for non-cart lightbox-display needs in the rest of your site; this can be done like so:
<a href="javascript:EJEJC_show('/url/goes/here.html', 'i', false);">Link text here</a>