I think they mean the scenario where the attacker sneaks in and adds a persistent backdoor / sets up privileged accounts for themselves to use / generally makes themselves comfortable, and then sits on their thumbs for a long period of time before activating the ransomware. If the victim restores from the previous day / week / months backup, the attacker can then sneak right back in and re-exploit whatever vulnerability.

The proposition then becomes "Our last non-compromised (as far as we know) backup is half a year old, can we afford to lose months of progress, or should we just pay the ransom?".

Or perhaps the attacker doesn't have a persistent foothold, but can make a credible claim that they do - do you take the risk? Keeping in mind that every moment you burn investigating and trying to discover the extent of the compromise is another moment you're down and burning money.