Sure.
Dan's explanation covers a lot of V-12's and they are not all seen from the same point when setting the firing order by the book. If he gets it right for the Sabre, bully for Dan. It means the number one cylinder was seen by the designers the same as Dan saw it. Nothing wrong with it if Dan's firing order agrees with the engine book.
But some designers look at the number one cylinder from the front of the engine and some from the back. If Dan's firing order disagrees with the book, the cylinders may be technically correct from a logical standpoint, but using the actual engine book will result in an engine that won't run or, if or does fire, may even damage the engine with reverse torque some gears weren't designed for.
If you want to look at the firing order from above the engine and from the same vantage point Dan's explanation is fine.
If you set timing on an actual engine that is to run by the data plate, then don't do it by memory or by ear or by hook or crook, do it by the engine book. If you are an engine designer, it makes little difference since you KNOW. Most people who overhaul WWII engines and actually set cam and valve timing are engine overhaulers, not powerplant engineers. They use the BOOK written by the engine designers ... and they get it right using both the data plate and the book.
You won't see Mike Nixon, Joe Yancey, Jack Rousch, or anybody else setting timing on a WWII aero engine that is to fly in an actual airplane without an engine book. If you do it by memory on an engine on a stand, so what? If you get it wrong, nobody dies and any subsequent damage or whatever is on YOU, and you're still on the ground.
If it is a flyer, the engine is worth some big money if it is a Merlin, Allison, Radial, or whatever ... any damage caused by other-than-factory timing settings is covered by your wallet. If that's OK with you, hey ... go for it. Your first mistake might cost you tens of thousands of dollars and if that's OK with you, then all is good.
If you KNOW which way the crank turns and which way each cam turns and which way the distributors turn, and how many teeth are on each gear and the size of the gears, adjusting timing isn't too difficult. If you aren't completely sure, use the factory engine book.
All the guys overhauling flying engines use the book and are required to do so by law. If you doubt that, just invite a local FAA inspector over to watch you jackleg the timing on an engine that is to fly without having and using a book and see what happens to your A&P license. That should be enough for anybody. You are supposed to have the book open to the proper page when you are doing work on an engine that will be bought off as flyable.
I'm not an A&P like some in here, but I know going by the book is required for aircraft unless you are in the experimental or experimental exhibition category. If so, knock yourself out with Dan's method. All the guys at Reno use a BOOK.
It ain't easy to get it right to start with and deviating can make it easy to require disassembly and resetting basic cam and ignition timing, but your time is yours, so go for it if the engine is also yours. If you are building an engine for a boat or a tractor or a car / truck / snowmobile then, hey, whatever you want to do is OK. If it runs, you're good to go. If it doesn't you can figure it out.
An automove V-8 has one distributor with 8 wires. A Merlin or an Allison has two distributors, each with 12 wires, and the intake and exhaust mags fire at different points. The automotive V-8 and the aero V-12 aren't necessarily each as easy to time right as the other one.