Agreed… The process groups docs say that it is app in one fallback case; the source code itself describes something fairly complicated:
// DefaultProcessName returns:
// * "app" when no processes are defined
// * "app" if present in the processes map
// * The first process name in ascending lexicographical order
It sounds like your own names might be beats and web—or something along those lines.
You might be able to work around this by just having an artificial app group that really means “release command Machines” to you, 
.
(@jechol, this might help a little with your question, as well.)