In that case probably someone modified it, to reduce port resistance. If there is high output bass then there will be a lot of airflow from the ports.
In a tuned enclosure, at tuning most of the sound comes from the port and not the speaker cone.
These are the ports on my bass lines. I used and open mesh metal grill each side. If you play an LT tone at power it will blow out a lighter.
This is the port of my in wall TL. It is the white grill to the left of the lower power amp.
The vent air velocity of a tuned reflex enclosure is of the order of 20 m/sec. That is a lot of air movement.
Back in the 50s before Thiele/Small, Gilbert Briggs in his books on DIY speakers, suggested tuning enclosures by playing a low tone and setting the port parameters by if it would blow out a candle! Yes, I followed that advice many years ago. Trouble is the first time I tried it, I had damped the speaker with cotton wool and the candle set it alight!