If the bores are Nicasil (or similar coating), then for the bore to become 'out of tolerance', surely the plating would have been stripped?
So, an out of tolerance piston/bore would be the least of my worries!
If the piston is wearing to that extent, it can only be down to 2 things as I understand.
1. Incorrect warmup procedures - usually leading to a 4 point seize on the piston, due to it expanding faster than the cylider walls.
2. Failure of the pre-mix oil to do its job correctly.
A lean mixture will cause the piston to wear faster, but the engine will usually seize before bore wear is noticed.
In both cases the piston will exhibit signs of scuffing/picking up. Usually evident by inspection through the exhaust port.
Any piston material smeared or left on the cylinder walls can usually be cleaned with a cotton bud dipped in acid. Usually spirit of Salts/Hydrochloric Acid, don't get on bare ally though!
On the RGV's I work on, you can normally be expected to get at least 3 sets of piston/rings to one coating of Nikasil (if undamaged).
Normal service intervals are about 10-12k miles for piston kits.
And these engines do spend time in the higher rev range.