Erm, we used one the standard VW 0.65mm shims and shaved it down
Your method is probably less of a faff! 0.12mm is what it had to be shaved down to to get it to fit. Yeah I’ve read the same about the input shaft but even with all of the shim slack removed, there is still play! I don’t track my car or thrash it, so I doubt mine will see the kind of stress & heat to seize the shaft. That bearing is barely even a press fit as I understand it. When things get really bad and the gear shafts start forcing each other apart, the outer race starts ovalising the casing.....which means a new gearbox anyway. This mainly only happens on aggressively remapped and/or track raced cars.
It wasn’t strictly necessary to do that to my new box but my OCD wasn’t thrilled by the play in the new box, even though it was signed off as ‘in spec’. I just know how sensitive the pedal & bite point are with shaft play, so did it anyway! My mechanic (who is a gearbox guru) said it would be fine, but on your own gearbox, obviously only do what you’re comfortable doing