What I'm saying is:
1. If "midori" began with the meaning "sprout", then...
2. its spelling in early texts should have been 芽 [sprout] and not 綠 [green].
The spellings were fixed a long time before the article identifies the change as taking place.
The Japanese spelling of a word must develop by either (1) the Japanese borrowing a Chinese word with the meaning of the Japanese word; (2) option #1, but the Japanese meaning of the word later shifts; (3) option #1, but the Japanese spelling of the word later shifts [this would be weird]; (4) indigenous innovation of a character; or (5) refusal to use a character at all.
"Midori" appears to have begun its life by being spelled as if it meant "green" and to have continued to mean "green" since that time. This is strange if it originally meant "sprout", and I'd like to know more about the claim and the history.
