I've noticed the same thing with AA schedules. I've had a few of my AA operated flights change recently. I chalked it up to merging schedules and finding efficiencies. Just annoyed my 1 hour layover turned into 4 hrs because they (AA) kept my original flight numbers. I'm sure there is no logic to bump me to the earlier connecting flight. I know a call will remedy.
I think we will be seeing a lot of schedule tweaks in the coming months.