If we're being pedantic, it may be deterministic from the point of view of Anthropic. They can guarantee that my prompt X results in actual prompt X+Y (Y being all the settings they control), which would hopefully result in deterministic output Z. From my point of view, Y may as well be random, resulting in non-deterministic output Z for my input X.

It is not deterministic.

It really though?? Even if you set temperature to 0 I saw research showing that the scheduling of the order of operations in the GPU firmware itself can change trailing decimals places and affect the output token

Everything might be deterministic if we are being super-pedantic.