EFATO Airbus FCTM
 

"The combination of high FLEX temperature and low V speeds requires precise handing during the rotation and lift off."

Low speeds makes sense as the controls are less effective.
Surely it would be a lower FLEX temp (higher thrust) that requires more precise handling. In this scenario more rudder will be required especially in combination with the low speeds than with higher FLEX temp.

Have I missed something?

Maybe they mean avoiding over-rotation / excessive pitch rate, i.e. loss of energy and tailstrike margins. Just a speculation.

Yes,the high flex reduces thrust and with loss of 50℅ thrust it requires gentle rotation to prevent loss speed. Since speed is also low the rudders requires more deflection to generate the effect as compared to high speed. Lower flex cause more yaw but higher speed compensates for it.

What you have missed is that it's not about yaw control. It's about rotation rate, speed control, and V2.

Try an A321 at 93.5T with a relatively high flex temp, and you will see what it's talking about.

Has anyone got an A321 sim though? We only fly the 321 but have to do our check on a 320 sim.

There are too many variables in the EFATO scenario for a "one size fits all" answer. Most of our performance generates 1+F figures that are improved climb. Some runways have much lower speeds but with flap 3 and TOGA. They are dynamic events that need careful handling to achieve a successful outcome.

I was reading for a sim session I have in some days and I read this just today. It made me wonder this very same question. I was thinking somewhere along the lines of what vilas said, a matter of low energy + low control surfaces authority

Have seen one in Zurich at swiss. Wasn't certified from the LBA though so we couldn't use it.

Today, GO5 will only provide an A320 datapack. Many, many years ago they would supply tail number datapacks and DLH, Swissair (as it was then) and maybe TAP received A321 FFSs. Now these sims are quite old standards and probably not possible to update.