Baerwald geometry gives the lowest peak distortion between any given maximum and minimum groove radii, in this case the modulated grooves of a 12" IEC record (60.325 and 146.05mm). FWIW the math was done by Erik Lofgren in 1938, before LPs were invented, but it can be applied to any size record/pivoted tonearm. It was 'rediscovered' in the late 70s/early 80s when SME and many other manufacturers started using it.
Technics used a different geometry, possibly weighting it for smaller inner groove radii (at the expense of increased distortion elsewhere), maybe loosely based on Stevenson geometry (a variation of Baerwald), then rounded it to the nearest mm overhang and degree offset angle. It's even possible that the published data is simply rounded and the actual geometry is different? Either way, both should give good results, but you shouldn't mix and match - if you want to use a Technics gauge keep the cartridge square in the shell and set overhang to the recommended figure, if you use a 3rd party protractor ignore the Technics recommended overhang and offset angle and set as per the protractor instructions and you can't go wrong
Regards,
JaS
