Interesting, I just dived into the same Garmin report. I agree, it’s saving and uploading the “Training Load” but not associating it with an exercise load or training effect. It’s really a bit all over the place just now. Hopefully this is all resolved with a better integration of First Beat after the purchase.
Edit: In fact i’m now thinking that increased Training Load is just from the TR activity upload, not from some mystery data hangover from a discarded activity.