12 minutes of eeg for 17 months baby with more than 70 myoclonus during eeg and they are all normal due to neurologist. still could be petit mal?

Unlikely: if myoclonus was of cerebral (aka brain) origin, it would very likely show up on EEG as either generalized epileptiform discharges. depending on the type of myoclonus, it can be benign physiological like hypnagogic vs from a lesion originating from a spinal cord (EEG would be normal) vs from metabolic, autoimmune, endocrine disturbances (EEG could show generalized slowing in some of these cases).