The top and bottom end both need protection, the oil is pretty much all cold and asleep in the sump. The oil pump is normally crankshaft driven and so related to overall RPM on most engines. So low RPM means low pump speed.

At cold idle the engine has some problems in this respect.

Low idle speed on most engines means low oil pump pressure so it is not quick to get around the entire engine
If the engine has been off for some time then the oil will have mostly drained out to the sump and cooled
No load at all during idle means it will take take some time to heat the oil to get it in best viscosity taking longer to become effective
With an even speed and no oil there may build up a wear point on older engines at a consistent point, this is mostly gone now
If cold the oil will not be fully viscous and so need some extra time to reach all corners (fully synth 0-40 was his fav)

I was told by a great engine builder to do the following.
1. Start and let idle for a moment to see it is smooth (it is smooth?)
2. Drive off with only smaller throttle opening for 5 miles (get some oil around it)
3. After 5 miles allow it to rev gradually with small throttle openings but up to 3-4000 on light throttle (get oil all over it)
4. After 20 miles you should be free to go.

This was said mainly for race engines with high compressions and slippery bits however it rang true for most piston engines when I considered it.

If the engine has not been run for a long time then run it on the starter without the fuel pump/electronics operational so the oil has a little head start if possible.

Yes modern oils are pretty amazing and should leave a thin film but the first scrape of a valve cam should fix that!
Yes a broader viscosity range can improve the situation but the warranty is dependant on having the correct oil and a modern engine wil not leave change from £10-30k if it pops.
Yes the manufacturer will vary the oil from market to market so ask your LOCAL dealer! Not an internet forum so getting an answer from Brazil for your car in Norway?

On the AMG I have an oil temperature gauge. I always use it for the first part of the journey. The 5.5L V8 is a huge lump with loads of oil and so needs long warming periods in winter. It always amazes me how long the gap is until it is above 70-80 deg in the morning. I can be out of Whitchurch and 20 miles North on the A34 on a light throttle before I am 70+. During that time I do little more than rest my foot on the throttle. Mind you with that engine that is plenty for most situations.

Everyone loves a Morgan. Even me, unless it's broken again.