Sorry it was actually 2 months. Just went back in my post history Sox pre/post was added Jul 1st.
Start of this season 28 teams were available. https://www.mlb.com/live-stream-games/help-center/subscription-access-pre-post-game
My guess is that NBC Sports Chicago got some pushback from MLB.TV. 28/30 teams were allowed on pre/post game when the Sox were still blacked out. It became available about 4-5 weeks ago. I noticed it immediately (as did some of us other non-Chicagoans)
It is a group or organization, but they are Mets fans. Met logo guy on their shirt and they all stood up and cheered when Winker hit the homer in the first. Several of them wearing Mets jerseys/hats. Looks like 2 lone Sox fans in the bunch