SE does have a Normal and Hard mode. Hard mode is 20~25 players. Normal is 30+.
The effect is the same. The fights all get easier, no need to worry about enrages or DPS checks, and less loot (per player).
It’s just weird that Blizzard is insisting on not having a difficulty setting that doesn’t require spending an hour in chat to recruit pugs. I guess someone there really wanted to give random puggies a way into SE groups? IDK.