One way to think about it is like artificial flavorings. The flavor of a cherry is complicated, so when a single chemical (usually benzaldehyde) is used to simulate the flavor of cherries or almonds, it’s a poor imitation of the real thing. It’s reminiscent of cherries because benzaldehyde is one of many flavor chemicals in cherries and almonds, but it doesn’t capture the full complexity of their flavor.

Similarly, a human experience like “winning” likely can’t be reduced to a single hormone or neurotransmitter. Brains and bodies are complex, so the experience of reward after winning likely includes many stimuli apart from testosterone - there are many subjective feelings and neurotransmitters/hormones involved in the struggle and victory, and these occur in a certain order during the experience of winning. The secretion of hormones and neurotransmitters is often local and has different effects in different parts of the body. Trying to achieve the same effect by injecting a single chemical is a bit like trying to swat a fly with a sledgehammer.

When the other cues of the struggle and victory are absent, it’s not surprising that even (a subset of) the same chemicals wouldn’t have the same effect. The brain’s expectations have a huge impact on our experience of events (consider the well-known placebo and nocebo effects), so even if we could perfectly simulate the hormonal effects of winning, a part of the subjective experience would be absent, so we might not expect the full effect to be present.

As for the god hypothesis… assuming one exists, he apparently has no problem with cheating, otherwise he wouldn’t have designed cuckoos to deposit their eggs in other birds’ nests so that they wouldn’t have to raise them on their own. Among thousands of examples where cheating occurs in nature and humans, often with impunity!