I really didn't want to fan the flames of this story more but I just want to add one quick idea quickly.
The old Code of Cannon Law was much stricter on the ordination of Eastern Catholic Bishops. The synod of the Church had to submit extensive dossiers to Rome for approval from the "Affairs of the Oriental Rites" (now, Congregation of the Oriental Churches).
In the new Code of Cannon Law, unless there is a "just cause" the Holy See Congregation of Oriental Churches does nothing besides approving candidates. They do the same thing with cathedrals. The bishops/synods of the Churches have authority to ordain bishops/designate cathedrals/etc. However, they have to notify the Congregation to obtain approval (which is normally granted). This is just a gesture to further emphasize their unity with Rome and keep correct count for the annuarium pontificium.
One recent example of the newly elected Patriarch of Armenian Catholics, His Beatitude Gregorius Petrus XX Ghabroyan. His Beatitude is 81 years old and way past the normal retirement age for bishops. However, the bishops synod elected him Patriarch. Rome has no authority or "just" ground to not approve his election and he was approved immediately.
I don't understand Bishop William/Ambrose's timeline well enough, but, if he was a validly ordained bishops, there will be a paper trail somewhere. The easiest was would be to check the annuarium pontificium for the year he claims to be ordained a bishop. His name should be listed.