Two close contacts changed the experiment
In December 1947, Bardeen and Brattain used nearby point contacts on germanium to obtain amplification. Surface states had frustrated a simple field-effect approach, and the working device made the semiconductor surface an active part of the investigation.
Shockley’s subsequent junction-transistor theory offered another route to controlling carriers. The joint 1956 award covers semiconductor research and the transistor effect; it does not make the point-contact and junction devices identical.
Gain must be measured in a biased circuit
A change at the input modifies carriers collected by a separately biased output. Voltage and current measurements establish gain only after the source and load are specified. A passive resistance change alone cannot supply amplified signal power.
Junction output curves reveal useful operating ranges
In a junction transistor, a thin base allows many injected minority carriers to reach the collector. Output curves distinguish an active region from cutoff and saturation. Gain changes with bias and device construction, so it is not a universal material constant.
Sources: [2]
The new Lab follows the junction device
The output-characteristics Lab connects carrier control to a collector-current sweep. Its junction model explains bias and saturation. The historical point-contact result remains a separate experiment whose geometry and surface physics are described in the original accounts.