I actually am not entirely certain that the bold is true, but it's because I believe that the real root of the thing comes back to misguided feelings on Tucker as well as misguided feelings on Ballesteros.
When it comes to Tucker. I think many have resigned themselves to this as a one-and-done year, In other words, he's not a "real" Cub to many. They have decided that his August is somehow the real Tucker, or that he couldn't possibly DH on a nagging injury. We have seen the fanbase at times look for reasons to throw fits about him at any moment since July.
On the Ballesteros aspect, I think an old Family Guy skit explains the concept really well but rookies who we have little MLB sample size exist as a mystery box that could be anything to many of the fanbase and Ballesteros is that mystery box. He's had some recent success too - success I'm a little wary of being capable of being replicated against the best pitchers in baseball (who you should expect to face almost exclusively in the playoffs). And because he'll be with the Cubs for the next six years, he is the future.
Combined, I think the injury is a cover story for what would be happening if Tucker was slumping as well. That's not saying you're doing that, but I think a lot of the root of this comes down to all of this. I don't think it's always conscious either.
For the record: Kyle Tucker over Moises Ballesteros is the correct choice barring him being so hurt he can't swing. Tucker was 20% better at hitting MLB pitchers than Mo Baller was at hitting Triple-A pitchers.