>> The meaning of ▼ being "Not in 常用漢字表". You could, at >> a pinch, take ▼ as also meaning "Write this word/kanji in >> kana". In which case ほうれん草 is as, or more, official >> than 菠薐草. I think that's a bit of a long bow, given the advisory nature of the 常用漢字 kanji these days.
Not really, it's just arguing over which of two possibilities which are _both_ rather unofficial is the 'least unofficial'.