I think the veteran owners are trying to make two key points for newer players:
1. Statistical performance will always vary somewhat within a given sample of PA, but a small initial sample has no bearing whatsoever on future performance. A player with a .300 normalized AVG is always going to be that in future PA, even if he's currently hitting .200.
2. Unless you made poor draft choices initially or find your situation very different than expected (i.e., drafted a bunch of home run hitters in Target Field or your division is loaded with deadball pitching), there is a penalty to using the WW and so there is no "extra cash" at all. In fact, it's the opposite. It's a salary penalty. So you'd be basically downgrading your roster and should only do it if you can get someone much better suited to your situation you find yourself in, so much so that it outweighs the salary cut.
All things considered, the best thing to do is almost always play out your existing roster. Underperformance is usually just about sample size anyway.
The only exception I could see is if you drafted way more IP or PA than you needed and could cash in the wasted IP/PA for a much better player you'll actually use. But again this is something you learn as a new player. I overdrafted on IP and PA routinely for my first year or so because I was so afraid of fatigue, and as a result I fielded inferior well-rested teams that lost more than they needed to.