At a glance, this question seems to be asking about "how to phrase my email", which is off-topic here. However, I believe we can edit this to fit the scope of IPS by changing the question to "what are the guidelines to write this email".
The goal is pretty clear. How can we salvage this question?
Update: the question now has been clarified by the OP. What he's asking is "should I thank them for choosing to accept the interview, when they haven't done the interview yet?", which is a question about etiquette rather than "how to write" or "phrasing request".
Can we reopen this question?