I pushed for this when I was a platoon leader and one of my commanders did, as well. It was partly for reasons cited in the article and also due to the fact that the division was way overstrength after our first deployment, due to stop-loss and stop-move. Gates to get on post were backed up for miles from about 0500 to 0600 and then the entire post was gridlocked immediately after PT. We wanted to save our Soldiers hours of time in the morning and then spend only an hour or so in the afternoon instead. The consensus view against us was...
1) the chain of command feared that if we broke from our routine then units would find excuses to let Soldiers go home early without doing PT; if not all units do PT at the same time, then how would leaders check up to make sure it was happening? (You can't make that up).
2) running would be "unsafe" because roads would not be closed off (as they are in the morning) and other units are racing home at that time
3) having some units do first formation at 0600 and others at 0900 would complicate accountability (I guess accountability of personnel is handled at division???)
4) We would lose out on the sense of espirit de corps that we apparently get by having everyone do PT at the same time (I never really felt any sense of espirit de corps when my platoon would run through the CSS area and pass by couples who spent their PT hours walking around and holding hands or sitting in their cars and listening to the radio).