The pads glaze easily as they gently rub against the discs during regen braking. The mechanical braking seems to be more engaged than other hybrid models which result in the noises, which get worse over time. Heavy braking now and again can help, and given that loan vehicles sometimes get some spirited driving that may explain the lack of noise you experienced.
I've had a very new loan vehicle and it was fine, others have been more noisy. My local dealer striped down my pads, re-greased and cleaned up the friction surfaces which resolved the issue for a few month and now it is noisy again.