I agree exactly
That's exactly why I don't agree they are engaged.
The next step of their life together is engagement. There is little reason, other then people's obsession with an African proposal, that they would hide an engagement for how many months.
Engagement is indeed the next step. A step they will take when she is done her commitments and moves to London to be with him. I have no doubt they have a promise to be engaged already, an understanding on a time frame. But I also don't get the whole, she is been hiding a ring for months, thing.
I think people just seem so anxious for a wedding. And seem worried if he proposes in December, that they will keep it private for a few months which will delay a wedding. There is no need to believe that or think that. And no chance of a wedding realistically before at least end of May either way.