From the UMP installer log file C:\temp\ia\ump.log we can see that the UMP installer found an old installation of the UMP on the primary hub:
Checking for robots already running UMP...
/<UIM domain name>/<UIM primary hubname>/<UIM primary hub robotname>/ has probe (wasp) active=1
/<UIM domain name>/<UIM primary hubname>/<UIM UMP robotname>/ has probe (wasp) active=1
Checking for "ump" pkg on robot with wasp [/<UIM dommain name>/<UIM primary hubname>/<UIM primary hub robotname>]...
got version of package ump = 8.40
NimBUS version 8.40 parsed to 8.4.0.0
Found robot [/<UIM domain name>/<UIM primary hubname>/<UIM primary hub robotname>] that has UMP [8.4.0.0]
Set $UMP_ROBOT$=/<UIM domain name>/<UIM primary hubname>/<UIM primary hub robotname>
Set $EXISTING_VERSION$=8.4.0.0
Set $MODE$=Upgrade
Since the ump package was installed on this robot at one time, the UMP installer detects that this is an upgrade, will install the UMP on the primary hub by default, and will not prompt for a robot to install the UMP on.