Is this true? In my opinion, no. The reality is that the Japanese culture, the people, in general, do not want to put things in their homes that other people have owned—especially things like furniture, musical instruments, or clothing. What do you do with a perfectly good, modern, moderately used piano that has little or no value in the domestic market? You ship it somewhere else in the world where people will welcome it, as an instrument of value—and buy it.
The Yamaha Corporation sees these pianos as competition to their authorized new and used sales, and treats them as such. No surprise there.
Yamaha makes, in my opinion, the finest mass-produced pianos in the world. I maintain dozens and dozens of them, and have worked on hundreds. I like very much, and in some cases, love, the pianos. They are extremely well-made, easy to work on, and can be made to sound and feel wonderful, especially the C series pianos of all ages, and of course, the older, hand-made “S” series, and the new CX series.
I have deep respect and affection for Yamaha—and I know the pianos they make are excellent. “Gray-market” or not. Enough said.