The only reason I could think of for doing this is if there was a problem venting the system or someone who likes the smell of sewer gas.
What is the plumbing code for ratio of drilled hole diameter to hole spacing on various diameters of pipe.
You just gotta love the DIY’ers, (that’s Destroy It Yourselfer).
I must say. In the decade plus of service plumbing I’ve never seen that one yet.
Nothing wrong with the smell of sewer gas. It’s usually the smell of money to a plumber. Of course, I can hardly smell it anymore.