This summary is not the rule. The rule text controls.
Here's a plain-English summary of Rule 1971:
A judge can order a new trial in a case that has already gone to trial. This can happen if one side asks for it, or the judge can decide to do it on their own without anyone asking. The new trial doesn't have to cover everything. It can apply to just some of the people involved in the case, or just some of the issues that were argued, or it might just mean the lawyers get to argue the case again without redoing the whole trial.
If the judge only orders a new trial on part of the case (like one issue or one party), the judge has the option to pause the entire judgment. This means that even the parts of the case that aren't getting a new trial might not become final right away. Everything can stay on hold until the new trial or reargument is finished.
This rule gives judges flexibility. Instead of being forced to redo an entire trial from scratch, they can fix just the part that had a problem while leaving the rest of the case intact.