You are probably correct. I'm using roads and building construction when looking for updates. I'm sure GM will catch up soon.I think that depends on location. For my neighborhood, GM is 6-12 months old while AM is 12-24 months.
I am dating this by road construction / improvements that have occurred over the last year.
Actually I just checked a construction area and AM is more like 18 mo. old. Still beat 4 years!