The whole experience of creating sandbox accounts is broken.
First of all, Safari asks if I want to save the chosen password by replacing the current App Store Connect, which makes no sense, as it's not my actual Apple ID.
Secondly, attempting to add such an account, sends an email to that account that reads "You have changed your Apple ID email, click here to verify".
What!? I don't want to change my Apple ID email. What makes anyone think that?
And anyhow, when clicking on that weirdly worded link, it takes me to appleid website, and no matter what password I put (either the one I put in the textbox when creating the tester account, or my real password), it just says "unable to verify".
Come on Apple, what is this..?
Also: I never heard back from you, regarding the Small Developers Program, or whatever it's called, which would let me pay you 15% for every purchase, instead of 30%.