Having a camera within the affected S/N range doesn't mean your body will have the issue. Manufacturers track the parts and stations used to construct every camera. Whenever a problem is discovered with a given batch of parts or a specific assembly station they'll check which cameras were built with those parts or at that station. Part defects or assembly errors are typically not 100% occurrences within an affected batch but instead a subset, usually due to an inconsistent use of process or variable quality of raw materials. Manufactures typically have no way to determine which specific articles within the suspected batch have the issue, thus the recall is issued against the entire batch.
The question I have is has Nikon clearly indicated whether or not you may be vulnerable to the issue over time even if you aren't seeing it today. If they don't answer that question definitively then I think it makes sense for most people to send it in to avoid running into the issue in the field, on vacation, etc. It could also be an added hassle if you sell your Z8 one day. On the other hand, if Nikon says you won't have the issue later if you don't have it now then I'd probably skip sending it in.