The holes are important! Atleast from my personal experience. It is important that those holes be clear when you insert the cup after every wash. I have experienced that if the holes get blocked (during the initial chunky phase of periods) the cup won’t fill and it’ll overflow or create pressure on my pelvic.
There is some physics in the importance of those holes.
I also tried a new cup with less holes and swanky design – nope! After an hour I’ll feel the pressure on my pelvic and it’ll pain a lot. I switched back to my older cup.
Most menstrual cups have holes near the rim that are designed and placed strategically for the purpose of sealing the cup’s suction mechanism when placed properly in the vagina. Some cups have 1 or 2 while others have 3-4 holes (it is dependent on the shape of the bell and the specific design of the brand of menstrual cup. And again the holes or amount of holes in a menstrual cup may assist with better sealing of the cup or it may be a feature that someone does not like about a particular menstrual cup. It is all about preference and ease of use vs. effectiveness for the individual’s circumstance.