The element of surprise

1. When we read the Gospels, some of the fulfillments might seem like a stretch. Indeed, unbelievers routinely claim that the Gospel authors gerrymandered the fulfillments. I'll return to that allegation in a moment.

However, it's also becoming fashionable in some academic circles to classify the Gospels as fictional by design. The authors never intended to narrate sober history. 

But that generates a dilemma since these two objections pull in opposite directions. If the authors of the Gospels were simply fabricating tales about Jesus, then they could easily invent stories that directly correspond to OT prophecies. The fact that the correspondence isn't always immediate but requires some thinking to see how they got there means the authors of the Gospels were constrained by facts about the life of Christ. 

2. I'd add that a basic problem with classifying the Gospels as fictional is that if that's that's the case, they were written for entertainment value, yet they aren't very entertaining. Some of the miracles and exorcisms might be entertaining to an ancient reader, but the Gospels contain a lot of moral ugliness. Lots of stuff that's not entertaining. Is the Sermon on the Mount entertaining? Is the Upper Room Discourse entertaining (Jn 14-17)? Are the Passion narratives entertaining? Just compare them to the Odyssey, Argonautica, and Ovid's Metamorphosis to see a truly fictional ancient genre.

3. Considering the other side of the issue, announcing the future is balanced on a knife-edge. It's necessary to preserve an element of surprise. If the oracle is too detailed, it can be thwarted. If a war plan falls into the hands of the enemy, the operation will fail because the element of surprise has been lost. Indeed, the enemy will turn the other's side war plan into an ambush. 

4. As a result, Bible prophecies aren't a roadmap to the future. They give the destination, but not the route, with road signs and intersections. If Bible prophecies were too detailed, you could falsify the oracle by changing a link in the chain leading up to the predicted fulfillment. Change a key variable to change the forecast outcome. 

In order for Bible prophecy to be feasible, it must be sufficiently specific and/or naturally antecedently improbably to be recognizable in retrospect, but be strategically obscure ahead of time. As a matter of necessity, the correspondence between prediction and fulfillment can't be too transparent. 

5. Finally, the argument from prophecy depends on the cumulative impact of multiple independent oracles converging on the figure of Jesus. So even if individual examples are somewhat elliptical, when it's one after another, that's overwhelming.