I am taking the liberty of CCing Reuben because I believe this report
can be merged with bug#30213.  As justification, a recap and correction
of my diagnosis and solution from that report follows.

The async-shell-command-display-buffer toggle determines whether the
output buffer is displayed immediately or in the process filter, as the
latter should only be executed on process output.  The guard in the
process filter, however, has always required that the buffer (a) be
empty; and (b) have the same name as the original output buffer.