When I import photos taken with a Sigma APO 50-150mm f2.8 II EX DC HSM lens they show in the metatdata as a Sigma 70-200mm EX DG Macro HSM II.
This is with the latest version of LR on a Windows 10x64 PC. It happens everytime I do an import to every single photo taken with that lens. Photos taken with Pentax lenses are fine. The body is a Pentax K3iii.
I can put the correct lens in the Lens Corrections, I believe I can change the actual metadata with EXIF TOOL, but none of that should be necessary.
"To add, ExifToolGUI shows the Lens Type for the Sigma as 'Sigma Lens (8 255)'" This sounds like a problem with your camera and/or lens combination and not a LrC issue. LrC uses the value for the camera and lens type from the MAKER NOTE tags in metadata.
The camera model is new this year, I've put the latest firmware on and it didn't make any difference - the EXIF has the 255.1 lens not the 255.3 lens and the LensType shows as 'Sigma Lens (8 255)' in ExifTool.
I did find the ExifTool page you refer to, specifically:
'8 255' = Sigma Lens (8 255) '8 255.1' = Sigma 70-200mm F2.8 EX DG Macro HSM II '8 255.2' = Sigma 150-500mm F5-6.3 DG APO [OS] HSM '8 255.3' = Sigma 50-150mm F2.8 II APO EX DC HSM - this is what it should be '8 255.4' = Sigma 4.5mm F2.8 EX DC HSM CircularFisheye '8 255.5' = Sigma 50-200mm F4-5.6 DC OS '8 255.6' = Sigma 24-70mm F2.8 EX DG HSM
I wonder how I report this to Pentax? The camera is a new model this year.