It says the agreement is done because it is, they are no longer negotiating and the terms of the agreement are set. Then it says, "The two companies expect to finalize and close the acquisition agreement within the next 60 days."
PR: agreement done, expect 60 days to execute terms of agreement.
8k: Must execute terms of agreement no later than April 30th.
I believe you are misinterpreting the process. Completing the agreement is like getting a signed contract on a house. They spend months in DD and negotiating terms, now that's complete and legally binding agreement contract signed. Milestone accomplished.
Next they execute the terms they agreed upon before the official close. Just like you execute the terms of a home purchase agreement before you officially close. They were clear and stated they expect it to be done within 60 days, clearly pointing out that part of the process was not yet completed.