Is such accuracy even needed? Off the shelf crystal resonator will have about 50ppm initial skew. Even assuming constant ambient temperature (which it is not, worse even there are thermcal cycles when the device is turned on and then off) there will be about 10ppm shift every ten years. It's faster when the part is new and tends to slow down and stabilize as it gets older.
The frequency can be somewhat changed (and hence corrected) with a small variable capacitor but I really doubt getting it within 10ppm or so tolerance was a part of manufacturing process...
Sure, most of the PCBs produced are very similar to each other but every now and then there is a black sheep and it's crystal is way more off compared to the rest. That would mean the game requiring very precise timing would not work on that particular piece of hardware... In that case you can claim to emulate said kind of unit and explain it not working is normal behaviour
