I suggest to ensure it's a p2 bug and to facilitate its remediation, you build some dummy test p2 units (such as empty bundle) with a p2.inf file using a simple
instructions.install = org.eclipse.equinox.p2.touchpoint.eclipse.addProgramArg(programArg:-consoleLog);
instructions.uninstall = org.eclipse.equinox.p2.touchpoint.eclipse.removeProgramArg(programArg:-consoleLog);
and put it into some p2 repo.
Check metadata, try installing then uninstalling it (really uninstall, no update).
If after uninstall the `-consoleLog` persists on some OS, then you can report to p2 with more details; if it does not persist, then you may need to investigate a bit more, but it could be caused by Windows not being able to delete open files, and probably altering the uninstallation process.