Indeed, the point there as you don't need a planter. Literally just a plastic bag of soil bought from a hardware/gardening store.
Of course the "new soil" would be full of nutrients, etc, it was more that this is possible even if you don't have a garden, or other hardware. (Similar intent behind mentioning the use of buckets!)
> People grow them in very poor soil, and even in literal bags of compost
a bag of compost is pretty much the exact opposite of "very poor soil"; it's about the richest soil there is.