This is one of those deals where there is a big difference in the compression test and a leak down test..
The compression pulses happen so fast that this size opening is not likely to show up on your guage... ( it being so small that you would not go looking for something,, as compared to just thinking your engine is gradually losing compression, which is normal ) .....

But a leak down test might really show up this if it is a burn through...and also... since a leak down test is way quieter when happening you might actually hear the air escaping at the injector.