Did they actually drill? I skim-read multiple sources about this and it isn't clear whether they drilled or whether there was an existing gap in between the ch

Did they actually drill? I skim-read multiple sources about this and it isn't clear whether they drilled or whether there was an existing gap in between the chevron blocks to insert a borescope. If it's the former then it makes sense to make 100% sure before drilling into a one-of-a-kind historical artifact, but if it's the latter, why so much effort instead of just trying the borescope approach to begin with at the earliest suspicion of a void?