Torpedoes are fairly complex.i might be wrong but it seems like if they couldn't guarantee working torpedoes then there's no way they could guarantee working thermite artillery, which is way riskier to carry
It requires a detonator, an engine, fuel, and a gyroscope at the minimum.
Additionally, the shock of entering the water can damage and disable the components.
Torpedoes only drastically improved around the 1900's, even though they were introduced around 1860.