With PL5.3.0 (Windows):
When I edit an Olympus OM-1 ORF file and export as JPG all the Olympus Makernotes are not exported.
With E-M1 Mark III it is working correctly.
Could this be because the company was renamed from Olympus to OM System?
See also here: EXIFtool Forum: new MakerNote header “OM SYSTEM II”