Don't have it reset where I am when I hit the back button on the page in the store. Hate sites that do that. It is totally inconvenient and has stopped me from making purchases before from sites that have that. It doesn't always happen on GOG but it happens enough to be annoying.

If you mean it won't take you back to the page you were on and instead takes you back to page one, then yes that is annoying and should be fixed.

That would be likely due to the JavaScript they use in some areas (i.e. Library, Wishlist).

The default BACK button of your browser doesn't really cope with the type of JS sometimes used on websites.
With your Wishlist for instance, you are clicking a button or link provided by the GOG website, that runs code that the browser BACK button is not privy too, so as far as it knows, you are still on the same Wishlist page ... Page 1.

Something like that anyway, though no doubt frames etc also play a part.