It is not so cut and dried because it is not so important at all.
On the internet, you will find people to argue about ANYTHING. And whichever side they take, they will put great energy rationalizing reasons for their choice.
Outside foil makes darn little difference in a guitar amp. I makes a lot more difference in say a short wave radio, which our guitar amp is not.
I like my parts to face the same way on the part board. To me that cosmetic difference is worth more than some outside foil argument.
On the other hand, if you pick one approach, and defend it to your death, you won't be wrong.