If I'm recalling correctly, something similar happened to a few people last year in late summer/early autumn. Is it something to do with new schedules loading?

I've only had routing changed once, and not nearly this close in. More like a month before, I think. The agent I spoke to to get back to my original routing thought perhaps it was to shorten my journey, but couldn't find a reasonable explanation in the notes. I explained that I had routed through DFW rather than ORD in January in my own attempt to 'shorten' my journey. I didn't get my original seats, but did still go through DFW.