This summary is not the rule. The rule text controls.
Lawyers can't file lawsuits or raise legal arguments just to waste time or cause trouble. Before bringing a case, defending one, or arguing a specific point, a lawyer needs a real reason based on facts and the law. This doesn't mean the argument has to be a sure winner. Lawyers are allowed to make honest arguments for changing, extending, or overturning current law, as long as they're making the argument in good faith and not just to stall or harass someone.
There's an important exception for criminal cases. If a lawyer represents someone accused of a crime, or someone facing possible jail time in certain other proceedings, that lawyer can push the prosecution to prove every single part of its case. This is true even if the lawyer doesn't have a strong argument that their client is innocent. The government still has to prove its case fully, and the defense lawyer can hold them to that standard without it being considered a frivolous or bad faith defense.
In short, this rule stops lawyers from filing baseless or harassing claims, while still protecting a defendant's right to make prosecutors prove their case in court.