All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
First of all, you should know that there is an old controversy among the scholars about both matters; we mean having witnesses when divorcing and when taking the wife back.
The view of the majority of the scholars about both issues is that it is desirable to have witnesses because they interpreted the order in the verse to imply desirability. The view we adopt in Islamweb and think to be the preponderant opinion is the view of the majority of the scholars .
The Shaykh whom you mentioned in the question –if he is a scholar –and he believes that the preponderant opinion is this view [which you mentioned in the question] and he issued a Fatwa accordingly, then he issued the Fatwa according to his Ijtihaad (a juristic opinion on matters which are not specified in the Quran or the Sunnah) and he is rewarded whether or not he is correct.
Since the issue is a matter of Ijtihaad, then the term ‘mislead’ which you mentioned in the question should not be used about it.
Allaah Knows best.