I’m not sure about the ten beat difference, but I suspect it has to do with economy. Either way, I would use the lower value ~160 for your AeT across all workouts regardless of RPE. Maybe even 155 as an upper limit to make sure you don’t exceed AeT when you’re training AeC.
On a related note, be careful about trying to be too precise. Thresholds are a moving target that will vary from day to day. It’s not that important to get AeT dialed in within a couple beats. It’s much more effective to know where it is roughly and then intentionally undershoot it.
“It’s better to be roughly right than precisely wrong.”
~ Warren Buffett