Version 1.67

Can the issue be reproduced?
Yes

Issue
Industrialcraft 2 tiny pipes can be created using 3 bronze ingots(made into bronze item casing) into 6 pipes, however they are treated as medium bronze pipes in the Tinkers smeltery(according to JEI) and melt down into 18 bronze total, very quickly allowing for infinite bronze.

Maybe late but this also works for the tiny steel pipes, giving infinite steel. I'm on version 1.69

So it is an exploit, but not as efficient as JEI states?

Tested it. melted 2 tiny pipes, and they produced 6 brozne

JEI is correct. PizzaAddict only used 1/3 of the pipes made. The original recipe for tiny pipes makes 6 pipes out of 3 bronze ingots/6 bronze item casing. Then the melting ratio is 1 pipe : 3 bronze, while the crafting ratio is 1 pipe : 0.5 bronze.