Yes, Paypal has already canceled the requirement to enter the developer's site in order to use the sandbox site ( fooobar.com/questions/1470323 / ... ). However, it will always run the "create new user" script. The error message will be around: you cannot use the cc number associated with a different email address (possibly from the payment information).
To remove this restriction, always log in to the dev portal before using the sandbox site.
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