Just to confirm my earlier confusion about verified snapshots at Compiling MySQL Tutorial 1 – The Baseline.
“Daily snapshot sources are only published, if they compiled successfully (using the BUILD/compile-pentium-debug-max script) and passed the test suite (using make test). If the source tree snapshot fails to compile or does not pass the test suite, the source tarball will not be published.”
Seems the fine print at MySQL Database Server 5.1: Beta snapshots also states this. Well, need to take my RTFM pill there.