I'm guessing you mean 917cc.
Oil holes are useful with fully floating wrist pins (gudgeon pins in the UK), where the pin is held in by circlips in the piston, and necessary when they are a press (tight) fit in the connecting rod. Some pins are a tight fit in the piston, often fitted with the piston hot, or just pressed in. In that case, there are usually no circlips, but an oil hole in the rod.
Your oversize pistons, if made specifically for this engine, I would expect them to be of the same design as the originals, in having oil holes. But the manufacturer may have decided that their pistons are better with a press-fit pin. It is likely that the pistons have been 're-purposed' from another application, being the desired size, and similar enough in other design aspects to be suitable.
If they are a good brand, they will be as designed, and should not raise any concerns.
