As I keep saying, they can simply NOT increase/scale/tweak anything.
Just a toggle to increase party size with the following note next to it: Combat encounters are scaled and balanced for a party of four. In choosing to increase your party size, you should understand that encounters may become considerably easier.
Yes, but that is like repairing a road full of potholes by putting out a roadside sign saying 30km/h (where you normally would drive 90km/h)
Nah. The metaphor would be more like:
There's a perfectly good 2-lane road with a 90 km/h speed limit (balanced 4-person-party gameplay). Larian adds another lane, with a divider separating it and the ^ lanes, that has a bunch of potholes and a 130 km/h speed limit (unbalanced 6-person-party gameplay).
You can still drive on the smooth 90 km/h if you want. All Larian has done is add another option for people who want to go faster, but they'll have a very bumpy ride.