This is actually a bug in my opinion, but since it’s been around for a while…
I think the activity log details should be in step with the automation history. Right now when a user pastes a new record or field for example, followed by an immediate undo or overwrite with another value, automations will fire on the pre-undo values.
You will not find these original values in the record history however as it doesn’t actually store / show changes when they are really close to each other. The result is an automation update that doesn’t make sense in the context of the activity log.
Needless to say this can cause discussion and hours of searching when you’re not aware of that ‘feature’.