They do not provide an additional 2500 MQD Headstart for card upgrades.
https://www.delta.com/us/en/skymiles...how-to-qualify
Card Members who upgrade from an Eligible Platinum or Platinum Business Card to an Eligible Reserve or Reserve Business Card will not be awarded an additional $2,500 MQD deposit for the Reserve or Reserve Business Card, and Card Members who downgrade from an Eligible Reserve or Reserve Business Card to an Eligible Platinum or Platinum Business Card will not be awarded an additional $2,500 MQD deposit for the Platinum or Platinum Business Card.