So for a 5x5 its 1200 watts at 50 watts a square ft..so thats the norm?
Height is important. 50 watts is really overkill unless you are hanging high for most even coverage. It will depend on lot of if you are running something like strips or boards etc. Also if the led has lenses and what angles. I would say at 30w per sq ft you are hitting a very good light point in most cases. If eunning co2 more but again its going to depend on the individual fixture and the height.
I have a 6' ceiling with an
hlg 600 that I can only run at 75%80% before light bleaching and to much stress when on 12/12. It covers a 4x4 fairly evenly. If ibhad more height i could run at 100% and probably cover a 5x5 no problem. Honestly I'm not sure where this 50w keeps coming from especially with how efficient most new led fixtures are.