Also from the article:

"Note that this is “run-to-run deterministic.” If you run the script multiple times, it will deterministically return the same result. However, when a non-batch-invariant kernel is used as part of a larger inference system, the system can become nondeterministic. When you make a query to an inference endpoint, the amount of load the server is under is effectively “nondeterministic” from the user’s perspective"

Which is a factor you can control when running your own local inference, and in many simple inference engines simply doesn't happen. In those cases you do get deterministic output at temperature=0 (provided they got everything else mentioned in the article right)