Update:
Below is part of the replied from the Platinum Concierge:
"However, after reviewing your account, I do show that the first agent that assisted you did advise you incorrectly. For this reason we will still honor the enrollment of the status challenge"

If I can summarize it based on 2 emails thread I had with them
- Once a member has been at the Platinum level, they are no longer eligible to take part in the status challenge
- Even if I do not successfully complete the challenge, I may still be upgraded to Platinum status once I have either had 25 eligible stays or 50 eligible nights posted to my account during the calendar year, January 1st to December 31st.

So.. I'll probably take this longer route since I have almost 8 months to achieve it.

Thanks everyone for the feedback and input