Twin Cylinder Head Tightening Perhaps a third possibility?

This 3rd example is how I have always torqued down cylinder heads on my Dommies.
After making sure that the pushrod ends are all correctly located with the cylinder head just softly  pinched down, I then go round the various nuts and bolts in increments of 5 ft.lbs until my torque wrench shows they are all at the recommended settings. 
I check the settings once more at 10, 100 and 500 miles.

Always torque the cylinder head on TDC to ensure the valve springs aren't absorbing the clamping torque. More importantly when re-torquing the head as the engine will never stop on TDC. 

That TDC thing is a new one on me.

I guess it comes down to whether or not the spring force is significant, in comparison to the clamping force of the fasteners.

Absent some radical alterations to the cams, I think you will find that at least one cylinder will have both valves open at TDC.

... that they went to all this trouble at Bracebridge Street or even Plumstead!

I understand where you are coming from, however I think 5ftlbs is a little too low and may not overcome static friction towards the end of the procedure. 

Increments of about that, work OK for me.

 I think the small  increments give time for things to compress ,and also also help to avoid silly mistakes that can strip threads !.