Might this "submit" just be a variation of the busy indicator?
It is actually a variation of busy indicator and the value is picked from Submit field value of type pyMessageLabel. I was assuming that overriding this field value should actually fix the issue but there seems to be some other problem with the code as it is not picking from the field value internally and just returning the field name as it is.
As Ron suggested can you check if overriding the js helps here, it is actually called from submitDrillDown function in pega_report_summary js file where doFormSubmit is passing third param as the field value.
One other thing you can do is to override the default interval of time that elapses before the busyindicator appears. The default value is pega.u.d.gBusyInd.busyIndInterval and is set to 2000 milliseconds. If you set this interval to, let's say, 10,000 ms, then the report would finish before the busy indicator would display.
Of course, you would have to be careful to save the older value and then restore it after the report renders. Probably a script or scripts in userworkform could accomplish this, tied to whatever actions launch the report.