“...only the Church scholars would know about it.”
As a convert to the Orthodox Church, I was certainly taught about it. In 40 years as a protestant prior, I had never heard the term used. I think the term is commonly known and understood in Orthodoxy.
I would imagine in one way or another, the Orthodox would me more likely to come across it. Orthodox Churches are also national in character and national languages usually do not borrow foreign words to the same extent as English, so I would imagine that an English-speaking Orthodox Church would very likely mention it.
I was born and raised Serbian Orthodox and we of course use a Slavonic equivalent of homoousios, but not the Greek word itself. I did not know the Greek word until I read it a regular Orthodox article years ago. I would venture to say that an average Russian or Serb or Arab Orthodox would not be familiar with the Greek term, but certainly with the concept.
In my response to Salvation, I was really addressing the western side of the Church to which he belongs, where such a term would really be known only to a select academic crowd.