221xxx is from '66 and I don't think Leitz were multi coating in 66, at the least none of mine from that era were muti coated. Later lenses might indeed be multi coated.

Lots of people like the SC lens signatures, CV make their high volume lenses SC or MC to allow the customer a choice.

Not noticed my CV 90mm to flare, but that is subjective opine, e.g. depends on the scenario you use it in. Some of the Leica lenses were flare queens...