Endless pillager spawning zones

Whilst playing minecraft on a minecraft server my friend invited me to one of my friends had been noticing outside his house in a somewhere around 7 by 6 chunks area there has been constant spawning of pillagers. He thought nothing of it since there were only ever upwards towards 5 or 7, so he just put a massive wall around it.

This is where I come into the picture.

I had gotten bad omen and accidentally went into his base which he had a villager house in... ofcourse this triggered a raid, I told him to get back quickly to fend it off. But what we weren't aware of was that the constant spawns from the massive box would overlap. We fought pillagers for 4 days and nights ingame time, and killed around 500 pillagers, yet we never got to wave 4. they simply kept spawning. eventually we got the owner on and they completely removed the entire area that place is in and filled it with glass at the bottom,