The saying 'Cherry blossom is the best among flowers and samurai is the best among people' was established by the Edo period, indicating that the image of Japanese people that 'Flower' means 'Cherry blossom' had been established before that.
また「花は桜木。人は武士」という言葉が江戸時代までに成立しており、それまでに「花」＝「桜」のイメージは日本で定着した。