None of us know the exact wording of the March agreement, as it was never released.
This set of tweets comes from a labor lawyer not associated with baseball. It is long, 17 tweets, but it explains the situation well, IMO. (The guy needs to get a blog!)
Here is the relevant part to your question.
“the document from an MLB attorney admitting the March Agreement said exactly what the PA said it meant all along.”
The assertion is that MLB admitted in writing that the March agreement did not bind the players to renegotiate salary. Eventually, MLB gave up asking them, though the MLBPA had said it was a non-negotiable item from day 1. Weeks were lost, but it appeared the owners were ok with that since it meant lower financial losses.
The central premise of this column, just found b/c @dougglanville responded, is another misguided retrospective both-sidesism that finds "Shame on Manfred and Clark: staying safe should’ve been Job 1 on this negotiation – not a fanatical campaign to extract every last dollar." 1/ https://t.co/ICjW8oi8d0
— eugenefreedman.bsky.social (@EugeneFreedman) June 28, 2020
As far as my personal opinion, like I said, the owners had a right to define the length of the season. They took the minimum number of games they could to avoid a grievance they did not want to take the risk of losing (or at least being forced to share financial data they want to keep private). The players had a right to hold to the March deal for full per-game prorated salary. So 60 games (at most) is what we get.
The owners could have implemented a longer schedule at any time, but in doing so, taken greater losses. (Also, in the last few days, fans in ballparks later look more possible, and if so, the losses will be less.) In fairness, they also could have scuttled the season entirely, but they did not.
What approach would have been better for owners to protect the long-term good of the game and the value of their multi-billion dollar asset? I guess we will never know.