Tthe doc being referred to in this incident is for the legacy Operations Dashboard (Operations Dashboard for ArcGIS 10.3.4). For the legacy Dashboard customer won't not need to run the installer in the Portal machine i.e. they can run the installer in any machine, and then deployed the output files into the Portal machine.
Please note that the legacy Operations Dashboard is in mature support and will retire soon. We strongly encourage users to start using the new Operations Dashboard.