the extension is not a requirement but an option. As long he qualifies for the visa and he is happy to pay every 3 month the embassy will issue a new one.
i understand your point and was actually my intention that time but if you go for it and the person that need to cancel it refuse to do it and say it is not needed there is nothing more that you can do
i did it with non O after that and no issues. The day i went to immigration try to cancel the non B extension the IO told me it will be cancelled automatically once the WP letter cancellation will be issued and even if i believe that your mentioned procedure was correct i wasn’t on the position to argue about it, but so far no issues after that. Maybe could be an issue if asking same category visa (non b) in the future, this i don’t know
i have been scolded from immigration officer to try to explain exactly what you are saying. IO clearly told me that in the case i leave before the WP was cancelled simply show the WP cancellation letter to the border office at the airport and i’ll be granted an exemption of stay on the next entry. And my extension of stay automatically voided. It was like this and under the re entry permit on my passport the border IO noted that my WP was canceled on that date. Followed this procedure and no issues at all to re enter under new visa/visa exemption and requesting visa extension
it depends on the case. If he leave the country before the expiration of the extension and have his WP canceled before he re enter then not need to cancel the extension of stay as it will be cancelled automatically.
You can do it technically with no limitations under visa exemption but practically even if you spend only 1-2 days each visit every week at a certain point the IO will ask you to get the visa. For sure for a couple of months they will not deny the entry but be ready to be questioned and have return ticket ready to show. At that point better to apply for a visa to avoid problems but the question will remain as you will travel too frequently and for super short visits