In English, the construction "run these substeps in parallel: A, B, C" means "run A, B and C in parallel with each other". However, in specifications, it has the specific meaning of running A, B and C sequentially on a background thread (that runs in parallel with the main thread).
Assigning the phrase to mean the exact opposite of its standard meaning in English is... unfortunate.
In English, the construction "run these substeps in parallel: A, B, C" means "run A, B and C in parallel with each other". However, in specifications, it has the specific meaning of running A, B and C sequentially on a background thread (that runs in parallel with the main thread).
Assigning the phrase to mean the exact opposite of its standard meaning in English is... unfortunate.