The experiment was searching for something else
Lee, Osheroff and Richardson cooled helium-three using a cell containing liquid and solid. Unusual pressure changes appeared in late 1971 and were initially considered possible solid magnetic behavior.
The experiments reported in 1972, especially nuclear magnetic resonance, showed that the transitions belonged to the liquid. That change in interpretation is central to the discovery, rather than an inconvenient detail to omit.
Sources: [1]
Nuclear resonance located the changing component
The solid and liquid contributed differently to the resonance signal. Frequency shifts and their connection to the pressure anomalies helped identify where the new behavior occurred. Temperature, pressure and magnetic field were needed to distinguish the phases.
Fermionic atoms require a different pairing structure
Helium-three atoms obey Fermi statistics. Their superfluid state involves correlated pairs, with internal spin and orbital structure richer than a simple scalar condensate. The experimental discovery did not by itself determine every element of that order parameter.
The 1996 prize honored the discovery
The 1996 award recognized superfluidity in helium-three; Leggett’s theoretical interpretation was honored in 2003. The linked crossover model is a conceptual comparison for fermionic pairing. It has no helium-three resonance apparatus or full spin-triplet order parameter.