[vdr] Question about epg.data updating.

When VDR compares epg data to see whether its been updated, does it actually compare the show description/info data or just certain fields in the epg data entry? I'm guessing the latter because I've noticed that when I populate extended epg data, a lot of shows will have a generic description. I let a few days go by and the generic description is still there in my epg data but if I delete epg.data and re-populate it, the description is updated. This leads me to believe VDR isn't comparing the entire epg entry for changes but perhaps just changes with show name or so.

Can anyone add clarity to this? It's happened so many times that I can't believe it's coincidence.