From reading the articles I am not sure if there will be absolutely no play-by-play at all after the starters depart, or just very limited play-by-play announcing, with mostly "sports talk radio style conversation" during the remainder of the game.
It is experimental, so if it doesn't work out well it can be tweaked for the audience and given another shot the following week - and if it is a colossal flop, they can always go back to the standard format.
Preseason games can be tough to watch for the mass audience (as opposed to die hard fans who spend time on fan forums 365 days a year), so I can understand their inclination to try something new. While it has the potential to fail miserably, it also has the potential to bring more insight, analysis and intelligent to what right now is a relatively bland and nearly meaningless product (preseason games).
Why not give it a shot?