I reached out to Marriott support and THEY CONFIRMED
"
I reviewed your reservation and do see that on August 18, 2018 this hotel will change to a Category 6 hotel and the package eCertificate and you ordered will automatically attach to the reservation.
Should this not occur in a timely manner, please call Marriott Customer Care or Marriott Rewards to attach the package eCertificate after this date has passed, but prior to your arrival."