In 18.104.22.168 beta, raid mobs spawning inside another village are not claimed by that village.
Steps to reproduce
Step 1: Launch Raid test 22.214.171.124 beta.mcworld
Step 2: Press the button above the command block (give bad omen)
Step 3: Wait until the raid bar filled up
Pillagers are taken by the other village and thus the next wave in the raid starts as the village "lost" the pillagers
The pillagers will spawn, but the village at the top will not claim the pillagers and thus the raid will start the next wave
In this video of 126.96.36.199: Pillagers not taken in 188.8.131.52 beta.mp4 you can see the pillagers spawn but the raid does not start the next wave
But in 184.108.40.206, this does happen as you can see in this video: Pillagers are taken to other village in 220.127.116.11 beta.mp4
This mechanic is also applied to other "dwellers" (inhabitants) of a village. When a villager gets in another village, that village will "claim" the villager.
This also applies to iron golems, when an iron golem walks to another village, that village will "claim" the iron golem as its dweller.