The SOP of THR LVRs to idle was not mentioned at the Vienna Airbus safety conference that analysed the speed decay in high altitude cruise scenario. There was another one 8 years ago. Both over the same airspace (Iran) interestingly, suggesting local effects.
With speed decay at high weight max altitude, it is likely that as near as maximum thrust is set anyway. There will likely be no further pitch up moments from increased thrust as there won't be much. The most important thing with speed decay in cruise below GD is to descend. Point the nose down to gain speed and decrease the AoA and turn offroute/Mayday as required. Sure, IF the nose does not come down, THEN reduce the thrust but that's full UA territory, and questionable whether the OP's sim has that fidelity.
Refer FCTM>
PR>NP>SOP>150>Speed Decay during cruise.
"If the aircraft speed goes below GD with max thrust available in use, ... descend."
For those who have access - Airbus world - Safety Conferences>2018>Day 1>Climb and Cruise events. P28
"If airspeed reduces below GreenDot with the maximum available thrust in use, the only way to avoid the risk of increasing the angle of attack is to descend"
Alpha prot or not, pointing the nose down to reduce the AoA is the most important thing. Yes, reducing thrust may help that in an extreme upset, but it's not the standard SOP every speed decay and I would argue that there's negative training going on in the OP's situation.