For removing the top-link you must know name of the link to remove link. Register-link is for register-link link.
Here is Name list of top-link.
register-link Create Account Link
authorization-link Sign In Link
wish-list-link WishList Link
my-account-link My Account Link
Add below code in your default.xml remove the link. For example you want to remove the Create Account Link for that you have to add below xml.
<referenceBlock name="register-link" remove="true" />
Same goes for other link too.