Yokozuma - the demonstration I was given at the British Museum was by Alex Fraser, co-owner of East Teas. He's as passionate about the actual tea as he is about the ceremony. Since he only occasionally gives demonstrations he would have used matcha from his own personal stock, sharing what he himself likes to drink.

The lady you saw in Kyoto has her focus mostly on the ceremony, it's not really in her economic interests to select and prepare the finest matcha for guests who are only paying a modest amount for her services.

I know that prevailing received wisdom dictates that matcha is characteristically bitter but I've not found that to be the case when sharing matcha with people intimately connected with matcha growers who prepare it for pleasure.
Within Japanese tea culture there must be some particular divide that dictates whether one should "suffer" a little (like a smack to the head given to sharpen the concentration of those trying to meditate) and that the tea should be bitter, but not everyone is on the same side of that divide.

I guess it's similar with coffee. High end coffee can be extremely smooth but there are many who seek out and prefer a more bitter/rougher taste regardless (have to stop here, I know even less about coffee than I do about tea).