I never disputed why the dome is needed for incident readings and I have pointed out that some situations are best handled using incident readings.
+1
I totally agree, because of that some Sekonic meters are made to operate both spot and incident. Still a particular photograher may have prefer one mode or the other in some particular situation. Often, if shot is complex and important, we may even consider both readings to take a wise decision.
My point is that all of ones light meters should be calibrated for accuracy and consistency.
Yes... but regarding Apps using the on-screen light sensor we have a "problem", some phones have a diffuser on the light sensors and deliver a reading that's always very close to the one a (say) Sekonic incident would deliver, while other phones lack that diffuser and is reading is very directional, being very extra sensitive to the rays that come quite perpendicular to the screen, and less to the others rays.
In fact, if you select the wrong 1 degree to read, you'll get a worse reading than if you used center metering or matrix metering.
Of course, spot mode usually requires inspecting several spots and taking a decision, or spoting a well selected 1 degree, plus adding a correction. For example we may spot a very light caucasian skin and then adding two stops for the key illuminated cheek.