RH 390 RPM updates

Hello, all.

I work with Red Hat systems on both intel and 390 architectures. To keep
these images up to date, we mirror the RPM updates for both architectures.
The difference in update release frequency between the two architectures is
great, as could be expected given the popularity of one versus the other.
This is not a problem except when there is a major security vulnerability
discovered and a x86 fix is quickly released and no 390 specific release
follows. One example is the zlib off by one bug. A x86 rpm was made within
days, while no 390 has been created as of yet.

We don't have a problem building our own binary RPMs from source rpms.
However, I would like some clarification as to RH's update policy. Why are
some 390 specific rpms released and not others? How can I know whether
specific 390 rpms will ever be released at all? Finally, can I trust rpms
built with the "rpm --rebuild" command to run reliably on the 390?

Thank you,
Michael Lambert