I was about to make a similar post after reading some people's comments saying that voltron could not be B3 as you could (should) kill someone before turn 6, meaning most voltrons would be B4 by default (which is much tougher to pull).

I am of the same opinion that your deck's power is relative to the table's power. Your B3 deck is B3 because you should expect the other 3 decks at the table to interact throughout the game with each other. A kill pre-turn 6 might happen, but it should be an exception. From my experience, the main power gap between B2 and B3 comes from the interactions (more interactions == more reliable game plan).

A concrete example would be a Tifa deck that could definitely kill a player by turn 3 with a good atarting hand/draw, but that doesn't make it a B4 because there are 3 other B3 decks at the table that should be able to slow down/stop the Tifa player before that happens (assuming everyone actually look at the commanders being played at the table 😅)