Correct and agreed, hence my "but works" portion of the comment!

The notion of portability is Docker's bread and butter. With proper version pinning you _might_ get lucky with repeatability too. Most people anticipate repeatability to be part of portability, but it really is a distinct notion.

This fits with the usual definition of repeatable. Repeatable means that you can run the same steps, but if the steps are non-deterministic, repeating them doesn't guarantee the same result.

> it wouldn't be surprising if it does not build at all.

This part is a stronger point, and it's true. When you repeat something and what you get is not just a different version or variation but something with totally different or broken behavior, that seems bigger than an ordinary failure of reproducibility.