Painter help shows 300 L/m and 1/24 of a pipe.
300 * 24 = 7200 L/m.
Fluid Tank help shows 1200 L/m and 1/6 of a pipe.
1200 * 6 == 7200 L/m.
Those are consistent with the Pipe help text.
If we assume Pipe is correct, I see two possibilities.
(1) Pump actually pipes 450 L/m in-game (450 * 4 == 1800). Only its help text value of 300 is wrong. That would make sense - you'd need one Fluid Miner platform to fill 4 pipes and the help text numbers in Pipe, Painter, and Fluid Tank are all correct.
(2) Pump actually pipes 300 L/m in-game. Its help text is wrong and and should say "one fluid launcher can support 6 of these", not 4. That seems weird because it would mean you'd need 1.5x Fluid Miner platforms to fill 4 pipes, but at least the help text numbers in Pipe, Painter, and Fluid Tank would still all be correct.
If we assume Pump is correct, then the help text for Pipe, Painter, and are all wrong.
So, I hope that the bug is (1), i.e. it's just a help text issue in one place (Pump).