Looks like Swiss, smells like Swiss, tastes like Swiss. It must be Swiss.

BG1 = party of 6, D&D rules, D&D stats, D&D XP rewards
BG2 = party of 6, D&D rules, D&D stats, D&D XP rewards
BG3 = party of 4, D&D rules with many homebrew rules mixed in, severely nerfed D&D stats, severely nerfed XP rewards

If it's nerfed with 4, maybe, just maybe, it was meant for 6. Hmmm.