Followed instructions on STARLUX website: www.starlux-airlines.com/en-US/COSMILE/CardTierMatch
Sent application via e-mail and got denial a day later:
We regret to inform you that Platinum Card of American Airlines is not included in this program now.
If you are qualified with Platinum Pro, Executive Platinum Card or Concierge Key Card of American Airlines before 31DEC20, we welcome you to submit the request again.
on November 1, 2020