I'm not arguing for this anymore this DP, just putting it out there. Mass character claims are good when enough of the following are true:
- there is a theme split
- the pool of characters is limited (could be a hard or soft limit)
- character - role connections are not clear
If scum are forced to claim early, they open themselves up to counter claims; or they claim their real role, and out themselves through thematic analysis; or they have to claim an obscure character, which looks scummy; or they claim something off-theme, which looks scummy.
If the character - role connections are not clear, this also does not give away power roles.