Well, FDev didn't design the mode system.
Selective multiplayer has been about for some time.
Warframe has Solo, Friends, Public.
STO missions have Solo, Friends, Public.
Minecraft has Single Player, Invite Only and Public.
And didn't Diablo have the choice of using the same character for Single Player and Multiplayer?
Which is why I don't get how some folks are not used to this yet, the mode system has been around for a long time.
It seems fairly new to me, and it certainly feels like it’s more the exception than the rule.
Haven’t played either Warframe or STO, and Minecraft (which I rarely played in multi-player) doesn’t allow you to move your stuff between servers, AFAIK. Elite is the first game with open world PvP I’ve played where A) I don’t have to choose between binary PvP options, and B) I can move my stuff between “servers.” It’s those two factors that make Frontier’s mode system both fresh AND brilliant.