With over 80 immigration offices around the country it’s impossible to know each of their own peculiar takes on certain rules etc. That’s why we usually tell people to go to their own office and find out the specific requirements for an extension from that office.
The old rule of two exempt entries by land per calendar year vanished on July 15th this year when they changed visa exempt entries to 60 days.
Now there isn’t an official rule of how many land, air or sea entries you can do a year but entry is at the discretion of the officer you hand you passport to.
You’re confusing a Non OA visa and a Non O visa/extension off of one.
With the initial Non OA you get stamped in for a full year or as long as your health insurance is valid until. This means that if you bounce out just before the visa expires and have a new insurance policy for a year then you’d be stamped in for a “second” year. This stamp is not multiple entry and you’d need a re-entry permit to keep that date alive.
Most Non O visas these days are 90 validity and single entry. You’d be stamped in for 90 days and could then extend that for one year. This extension is not multiple entry so again you’d need a re-entry permit to keep the stamp valid.