with smaller nozzles you need hotter temps and slower print speeds.

It's all about viscosity and flow rate and cooling speed.

So hotter pla has less viscosity and will flow better - but with a larger bead it will also cool slower and slump, leading to issues.
with the really small bead it needs to be hotter to flow properly through the nozzle. And as it's such a small bead it cools quickly enough.

Running a 0.4mm nozzle at higher temperatures 'should' result in inconsistent layers as the pla slumps before it cools enough to hold it's shape.

The other ender we had was running pla at 240c.
I've got 5 different printers (hang on - 6 ! but the sapphire pro is beig rebuilt before I finish construction lol) and all of them print pla between 200 - 215. And that's a LOT of different brands and colours of pla.
So something is just not right with the either the creality thermistors or the heat cartridges.