Um, rpm headers are not compressed, so there is no decompression overhead retrieving a tag
value, and there is no reason why an entire rpm needs to be decompressed in order to
retrieve a value.
Presumably you are obliquely referring to deltarpm creation, not rpm tag value access.
After watching the video, I am also unsure how you got the impression that the number one
request was for faster access to fields in an rpm header.