It's still not clear they're following the letter of the licence. Here's what likely is happening:
1. RedHat work on the source in form A
2. Form B is auto-generated from A
3. Form B is distributed to comply with the GPL.
A is the src.rpm with the split patches: the format they've preferred for donkey's years and, I'm presuming to be a dead certainty, are continuing to use internally, and B is the src.rpm with the patches deliberately collapsed. Talking about email or conversations is a misdirection - binaries never get machine-built from such. The patches *are* a source input to the process that builds the distributed src.rpms though, and the reason they are an input is because that's RedHats' preferred means of making modifications.
Look at the flow above again, form B *clearly* is covered by the GPL through the text in which explains what "preferred form" is meant to cover. It's pretty explicit that intermediate transformations of the sources are *not* sufficient, that *all* the files required for input to the build process are required.
Just because an auto-generated file is still human-readable and editable does not take-away from the fact it's not the original source.