As you say, the current FAA allows each FSDO alot of lattitude, and if you have been around aviation long enough, I'm sure you may have even run across issues where one FSDO approves something only to be told later while in another region that your ticket, or your airplane are not airworthy, and the other FSDO made a mistake... I HAVE seen this happen personally, so I'm my own proof. The time I saw it was on a private plane with an IFR GPS installed and approved by a certain FSDO in accordance with an Advisor Circular guidance... the plane ended up in another part of the country years later, and during a prepurchase inspection, the IA didn't like the way the paperwork was done and brought the issue to the local FSDO for an opinion, who promptly grounded the aircraft... so, it DOES happen.

That all being said, how much simpler does it have to be. This reg says "performing the duties of PIC." The duties of PIC are not simply flying an airplane and programming an autopilot. The PIC signs the release, accepting the aircraft, the preflight planning, the load planning, and the physical fitness for duty of the crew... a FO does none of these things; hence you are not performing the duties of PIC.

That section is for people who are performing all the duties of PIC (baby Captains) that are technically not PIC of the flight, the IOE Instructor is.....

just as in the old days when (if) you ever flight instructed.... as CFI you were the PIC of the flight, your student logged PIC as the manipulator of the controls... and this reg does not say anything about logging PIC time as sole manipulator, it says by performing the duties of PIC, which FO's do not do.