Regarding package feed packages index I learned one difference between rpm and ipk.
For ipk plain-text files named Packages are generated and placed to architecture-subdirectories in tmp/deploy/ipk tree.
For rpm I see just one file named Packages, it is a binary file yet located in one image arch-subdir within tmp/deploy/rpm tree.

Is this difference the result how Poky/OE handles both
or rather coming already from package management systems?

I wonder also how could the chances be to have Packages files in RPM in same form
as for IPK - plain-text yet provided for each architecture build artifacts sub-tree?