When we assume that someone erases a timeline, we're saying that the assumption means that the flow of events are ceasing to happen, but generally I feel like fiction really accounts that the flow of events was also destroyed retroactively. I feel that unless you have a statement with a
vibe like this where the erasure is the entirety of time then it probably shouldn't default to Historical erasure.
Though having said that, this is not our default assumption. To quote our universe page
If you're rated as Low 2-C, the assumption is that time has been retroactively destroyed. Meaning that you'd also need to destroy it historically, which makes the power a default of our current system if you have universal timeline erasure.