Bismillahi Al-Rahmani Al-Rahim
The Qur'an And Non-Muslims
"Not-yet-Muslims are prevented from reciting the Qur'an, even if their entering Islam is hoped for / expected."
What about when Sayyidna 'Umar (radhiyullahu 'anhu) read the Qur'an as a mushrik?
What about the many scholars who have gifted Western rulers with copies of the Qur'an?
As for the first question, the event you mention took place in Mecca right before `Omar (Allah be pleased with him) entered Islam. The text of the hadith indicates that his sister (Allah be pleased with her) refused to hand the mushaf to him until he had sworn to Allah that he would not harm it and that he would give it back, and that once he did complied to this she refused once again until he had made ghusl. He (Allah be pleased with this) complied and upon reading surah Ta Ha he entered Islam.
I found this hadith related in Musnad Imam Ahmad but could not find it elsewhere, and I do not know the actual authenticity of the hadith. Assuming that it is rigorously authenticated, there are many possible explanations. To name just:
And Allah knows best.
wa al-salamu `alaykum