This is exactly the reason this is not a recall. (even though folks are not reading the paper correctly) Everyone effected should go back to the first page or read the document sent. This is a "Voluntary Service Bulletin" The same as the type that Yamaha issues for all powersport products with less severe issues.
A recall is more serious and is telling the customer that if they do not bring the product in, the MFG is not responsible for losses or failures and will cover correcting the issue.
A service bulletin is a notice to the owner that they may experience an issue, and you can voluntarily bring it in and the mfg will repair or replace the failure if you are actually experiencing it. But it may not be experienced by all. Sometimes, they will correct it even if it has not failed, but it is at their discretion. (sort of like the timing chain SB that was issued almost 10 years ago, it was never a recall and they did not have to honor it to anyone other than the primary owner)
These are, in fact, legal terms and both are for CYA purposes on Yamaha/Shorland'r's part. With powersports, a service bulletin many times does not mean the MFG has to do anything at all, if you are not experiencing the documented issue. That's why the owner is not calling the shots on a Service Bulletin, and it many times voluntary. But a recall is pretty much telling the owner, bring it in or we are not responsible for the outcome.
Some MFG's take it a step further and issue a stop ride/stop sale, where serious outcomes may occur without the recall being performed. All three need to be understood that you may not experience the issue/failure. So in this case, inspect and take the appropriate action, but you are not required to.