Here’s the comment I was looking for! I was going to suggest this might be the issue. (total guess), but it made sense when I saw its the standard size of other blister packs you get.
I also heard that the reason heinz tins dont stack well whilst other brands do is because of how expensive it would be to replace the machines (or parts of the machines) that make the can lids and bases.
So it was a fair assumption that it’s basically the same problem here.
Especially when you consider that it’s probably very few people that need just 1 of a certain pill. Thisnis likely a supply issue with this medication in the multi blister packs, so they gave 20 singles.