And what do you think is the algorithm from the article? Looks awfully similar to base64 to me, except its lacking the bit-shifts. Both use a lookup table like that.
I think a lot of this depends on if you read the article as the scream cipher being specifically the exact listed substitutions or just any substitution with forms of As. Also depends on how you define encoding, cipher and the overlaps between the two. Plus questions on the relevance of intent, transformation of data, plus changing of meaning and definitions over the years. Some people say morse code is a cipher, but braille isn't - definitions can depend on way more than the black and white logical "but it does this" you're using.
You'd do better debating this with a real life friend over a pint, rather than wasting your time trying to argue with multiple people here.
You will find that the pigpen cipher has a 1:1 mapping between its input alphabet and its output alphabet, and that a 1:1 mapping is a necessity for full invertibility.
What people in this thread call a "key" is, not like a key, auxiliary input data, but hard-coded into the program. We are looking at encodings.
Maybe this differentiation is not popular or well accepted, but it was surely part of my cryptography curriculum and the following exam. I'd rather believe my prof than strangers on the internet.
Base64 is an encoding. It's an algorithm, no attempt at secrecy, thus not a cipher.