AVCHD is a heavily compressed format. Any encoding to another heavily compressed format after treating it to AE can generate bad quality due to the compression losses stacking up. So, your wording seems OK to me, I'd call it crap too.
AVCHD at typical camcorder data-rates is not really a pro codec. If you encode to a format with milder or no compression, you can preserve the initial quality, but you'll need pretty beefy drives or a RAID.
Director of the Institute of Media Research (IMF) at Braunschweig University of Arts