I don't understand `75 1.2x10-12m` as an example of a scale without a unit, since it contains a unit (`m`).  I certainly would read the CDS standard to say that a unit is required, by rule 4 (though I admit there's room for interpretation).  The unity grammar implementation of it also seems to suggest a unit is always required:

https://bitbucket.org/nxg/unity/src/4459108fc29d37c6610b341d14100c17ae2a5527/src/grammar/unity.y?at=default