the reason for the switch to 3 groups is as follows:
1. Fewer games played in pool play
Had to have 30 matches in 5 days, so 6 matches a day (both sexes)
Now only 24 matches in 9 days, so 2-4 matches a day (both sexes)
2. More time gaps between individual matches.
Fewer matches mean longer breaks for working staff, FIVB and referees, media
3. 6 team pools often had meaningless last matches.
So with only 4 team pools, last matches mean something.
Prevents teams losing on purpose to get a better opponent.
With an additional pool, final opponent will be based on wins, points and sets ratio across all pools, 1-8.