...when the adoptee would/will be 18 years old

[Wingedfish]

Hello, everybody,
In the following sentences taken from the BNC:

1. British parents have to wait for adoptees to choose to contact them and may therefore experience feelings of desperation and anticipation around the time when the adoptee would be 18 years old.

2. You may not be able to retire when it would be most convenient.

why "would" instead of "will"?
Is that because there is the modal "may" in the main clause to indicate a kind of uncertainty? But I have also found sentences like these with "WILL":
3. This is under construction, you may find interesting when it will be completed.

So, what do you think of these sentences?
Thank you advance!

[Haihao]

Due to euphemism, I would think.

[Jamie (K)]

They're using "would" because they're talking about hypothetical situations.

[Wingedfish]

But why is that a hypothetical condition? It seems to me that there is no condition at all in these sentences.