I believe the only things that were retroactive to 8-1-18 were the economic parts of the contract.
Right, they weren't going to go back and make any other changes in regards to what happened before the new changes went into effect. Like they couldn't retroactively change new RPCD's to 22.4's. But the language about moving RPCD's to m-friend states specifically from the date of ratification.
The company knew the language was there, and had plenty of time to set a plan in motion. The only catch to this would have been in the case that the supplements were not ratified within 18 or 24 months, then the new language would not have been implemented in time for that provision to be fulfilled.
But as things played out, UPS has plenty of time to fulfill the provision. Could UPS argue that they need more time, and could the union grant it? I guess, if no RPCD's want to challenge it.