You don't understand what is being discussed here. The guidance was given to federal agencies to figure out how to make their research available publicly. There was no guidance given to publishers, they don't have to do anything. Read the memo. https://www.whitehouse.gov/wp-content/uploads/2022/08/08-202...
Yes the agencies will have to survey all the ways that their spending goes into research. Some of these will be obvious like NSF grants. Others will be more gray area like R&D contracts. They will have to modify the rules for each of these processes, and train employees on the new rules. There may be existing contracts that will have to be renegotiated. Some of the agencies may have legally mandated processes they have to follow when making changes to rules, which may include public comment periods. Many agencies will be able to make the change within a year, but some will have legitimate reasons for taking longer. Three years is generous, but not ridiculous.
