There’s an obvious reason, and it’s one more item in a long list of indicators the dev team has atrocious practices.
What do we know about the next version? Something is changing about Delves with respect to making faction v. faction fights easier. So we know they’re tinkering with the Delve code and it’s possible “easier matches” means “rebalanced rewards”.
When a new version is relatively close, and the new version involves tinkering with a game mode, it’s almost always true at some point that mode breaks in the “normal” game. GW gets wonky, PvP gets wonky, a troop we’re not supposed to see appears, etc. They usually fix it pretty quick.
But that suggests they don’t really have separate production and dev servers. Instead, whatever’s running on the server turns things on and off based on client version. If they forget to put a check for the version in, then some amount of that feature’s code runs for all of us. But since it makes different assumptions about the world, and probably not all of it is enabled, weird things happen.
So they probably have internally changed something about how Delve rewards are calculated in 4.5. It may not even be changed so much as “the data structure that describes it has changed and put the reward information in a different place or format”. The client gets all its data in the form of JSON. In general, when something parses JSON and expects a property that isn’t there, the only sensible thing to do is whatever your language analogue is for “undefined”. By default, the most common C# JSON parser uses “the default value” for a type, which is 0 for numeric types. Ta da! This is how we visually get a 0 reward.
The code that actually calculates the reward is a thing that pays players, so it probably got more scrutiny. That section of code is properly checking which version of code to use. Sort of. It gets the +3 from the hoard right, but is also impacted by the +0 instead of +1 from the other bit of code. Ta da! That’s how it sort of works.
“No separation between dev and production” is a pretty grade school project smell in terms of software development. Even middle school projects take points off for it. GoW constantly demonstrates why it’s a bad practice, from accidental releases of code to inability to describe what features are actually in a patch until the client is downloaded. I’d be surprised to find out they even have source control or a formal ticket system other than some post-its on a wall and zip files with dates on them.