Physical copy protection?

Hello

To keep it short, there was an Anime expo (really small) where some people where selling DVDs, so i bought one (these are burned DVDs, in my country it’s not illegal on Anime) anyway, i just found out i couldn’t read this DVDs in my burner but on my home DVD Player worked fine. So i took a look at the DVDs and physical they have two holes near the beginning of data, these holes doesn’t go from side to side, just on the data side, but you can clearly see there’s no “ink” in there (purple stuff). From 5 DVDs, 4 had these holes and i couldn’t read any, for the DVD with no holes, my burner could read it. Mostly than going into stuff like if my burner can or not, first, i want to know if this is really a copy protection scheme for burned discs?
Also, my Xbox can read it, so i can theorically copy them back to my hard drive, still, for the knowledge, i really want to know what’s up with these discs, first time i ever saw something like that.

Hope someone knows something.

Thank you.