Unlike the term “judicial activism”, which is simply meaningless, “legislating from the bench” seems to imply a relatively clear type of activity. Which is not striking down legislation.
Legislating generally means passing laws. Judges don’t pass laws, they nullify them. As Ambrose Bierce said in another context, “whoever drew the meaning from this excellent maxim and substituted a contrary meaning of his own has exerted an evil power which appears to be immortal.”