No idea if there even is a 75K platinum select offer (not to my knowledge), but I've sent the message below, and I've been successful 3/3 times last week:

Subject: Offer match request

Dear Sir / Madam, I hope you are having a good day! I was wondering if you could help me with something - I recently applied for a new Citi / AAdvantage Platinum Select World Elite Mastercard (ending in -1234) associated with the 65,000 miles AAdvantage offer. However, after I applied I saw online that the offer had been increased to 75,000 miles with the same spending requirements. Would you be able to match this higher offer for my account? Thanks for your help!