Experimental is autobuild, but on an best-effort basis
(which is a different thing than what happens with unstable).
In other words, it can happen that a package is not build on all architectures,
and nobody does anything to fix that.
If that happens to one of your packages, please contact us (Martin Zobel or me),
and we'll try to fix that.
I just have rescheduled glibc in experimental on two architectures.