If some or all of the foldable ranges in the file are folded, then the Toggle All Folds command in the Fold menu unfolds all those ranges, just like Fold|Unfold All does. Ranges that were unfolded remain unfolded.
If all of the foldable ranges in the file are already unfolded, then the Toggle All Folds command folds them all, just like Fold|Fold All does.