Those holes is where little rocks used to be to way down the product for bigger profits.
When selling, some people use sand, sugar, glass shards or silica glass to do the same thing. It's called "grit weed".
Seriously, I've had two friends hospitalized with severe chest pains from smoking such.
The purchased grit weed came from two different dispensaries here in LA (SFV). Some shops
buy it and sell it knowingly and some unknowingly. When buying from a shop
always bring
a (10x at least) jewelers loupe. Trust no one.
If you buy your cannabis on the black market, you risk purchasing something known as 'grit weed.' Here's how to recognize and avoid it.
wayofleaf.com