They're not bragging, they're saying it to counter the media narrative about them.

I think a lot of white collar workers (ie. journalists and people reading certain papers) are shocked to find out that warehouse/blue collar jobs are hard and not paid great. It says more about the reader than anything else.. I'd wager that conditions are a lot better at Amazon than at some random warehouse where people are working out of the media spotlight.

Also, if you have over 1 million employees, you can always find plenty of stories of things that went wrong, kind of like in a 1-million population city there's always plenty of stuff going on.