X I was testing with CC 2017 and Image Processor Pro did not record in an action like a plug-in. However old action I recorded IPP in worked like a plugin. I still use CC 2014 so I tested the other creative cloud versions of Photoshop recording a IPP Plug-in step into an action. CS6, CC and CC 2014 recorded the plugin step corectectly, CC 2015, CC 2015,5 and CC 2017 did not record the step correctly. I do not know if its a bug in Photoshop on not. For though CS6, CC and CC 2014. Record and plyay the step like a Photoshop Plug-in use the recorded settings the action step. The recorded action steps the work correctly look like an empoty step in the action.
It may also be worth pointing this out to xbytor:
xbytor at gmail . com
More testing shows it fails to record correctly in CC 2015, CC 2015.5 and CC 2017 if you include running an action in the Image Processor Pro Dialog. The Action step is not recorded like a plugin
If you do not include any actions the step will record like a plugin.