I watched that video recently and the conclusions were actually the opposite of that: James preferred the week-old coffee from the really good grinder over the freshly ground coffee from the cheap grinder. The testing carried out on “regular people” also didn’t show a statistically significant preference for freshly ground in this scenario.

The conclusion is pretty much: if you don’t have a good grinder, you’re probably better off buying really quality pre-ground coffee. At least if you can buy it in small enough batches. Obviously if you buy a huge bag and take over a month to use it up then yeah, it will be stale eventually.