Not trying to start an argument but personally from my own experience i feel that is an old throwback that has been losing ground for a long time if 8 truly was a significant barrier then we would not be playing 30 slot or even 50 slot servers without issues. What i mean is that there is many servers out there that run perfectly fine with 30 or more concurrent players irrelevant of what the supported max is.
realistically I would say pre hub city is the last time this held any relevance and towards the end of hornets around a15 def 16 was when the 8 player soft limit srtarted losing its reality.
Unless they actually come out an update the stance on this then yeah 8 is the max supported/recomended and the game is still early access so i think it is more of an over/undersight at this point than a hard requirement. Truly though if it was that significant then they would make it so that we are only allowed to have 8 players capped with the ability to have no more than that.
I use to play on a server that would average 50 players at any time and was perfectly fine it had good hardware though and have played several in the past that average 30 or more that also have no issues running those sorts of numbers.
I have hosted this game numerous times so i know how taxing it can be but if you have proper hardware then its not an issue.