I think the companys goal is to piss off the really senior dudes that have been here for a long time that don't want to leave because they have a great schedule with 16-18 days off a month. Even though the whole atmosphere here really sucks right now(for about the last 3 years really), they stick it out because great QOL when you are senior as far as schedules. With September, unless you are in the top 10 out of 400+, your gonna only have about 12 days off and some crap ass 4 day. Company trying to get these guys and gals to move on so they can get some junior people who are cheaper in there instead.
Kidding aside, I'm sure the real reason is, its most likely a combination of Delta's scheduling, the animosity toward the pilot group, the fact that we have no say in line construction and the fact that no one really gives a crap how many days off we have other than us and our families.
However if a by prouduct of these new lines is that some really senior people quit and move on, I'm sure mgm't won't lose any sleep over paying a replacement less.