It's not about "balls." It's a contract provision that was actually a loss from past practice.
The IPA had a long history of a very open policy of open-time and JA bans whenever they wanted, even during contract negotiations, and up to the early '00s, it was perfectly legal. Along came a judge in the 11th Circuit Court and ruled against the Delta pilots when they stopped picking up open time, and suddenly the law changed. When it came time for UPS/IPA to negotiate a new contract, UPS management said that the IPA's long-standing position that they could tell pilots not to pick up open time was now illegal, and the company wouldn't recognize it. As a compromise, the IPA agreed to the above provision in their contract, which limited the times that they could call for an open-time ban to just when pilots are furloughed. It was a significant change in their past practice, but it was the best they could do for a compromise. Unfortunately, I doubt they'll even be able to hang on to the compromise in the next contract.