For starters, the so called account steve looks like he/she/bot made it look like it was their story, which is a shitty ploy itself.
A young guy pic calling itself oldguy?
Anyhow, worked retail, didn't go to that twit so don't know/care about the issue, but it is indeed true that employees are instructed to be frugal, but with the customers need first in mind. Most people double bagging usually have real reasons to do so. The only time I remember years ago stopping someone is when they were stuffing unused bags into the bag they were packing. The smart way to do it is just double bag if you need bags at home. Workers even give people bags if they ask. Your day goes easier if you work with customers and not belittle them.