No it really isnt. You just take the definition too far.
The job of a support player is to make sure the stars of the team can get into advantageous positions and can focus on making plays.
Most teams do indeed have player(s) who fit this description. Its not hard to tell which players are sacrificial/passive and which arent.
The sacrificial players are almost always support elements whose job is to set up the stars thru a multitude of different ways. Xyp9x may not consider himself a support but if you look at his roles before joining this Astralis core you can see a clear shift in playstyle.
Just because someone is the support does not mean they can underperform, it just means that they are not set up the same way the star players are and therefore should not be judged as heavily on stats because they are given less opportunities to multi frag.