Isn't the Le Club Accor membership year Jan-Dec ie the calendar year?
So non-AccorPlus Member earns Platinum in the Calendar year 2019 by July 31st - Platinum status lasts till Dec31st 2020
According to the wording on the website quoted above:
AccorPlus member earns Platinum in Calendar year 2019 by July 31st , if their renewal date is say Sept 30th 2019 "you can retain this Status until the time of your Accor Plus renewal the following year" - Platinum status lasts till Sept 30th 2020. So you are worse off being an AccorPlus member - no?