On the models that are affected by this limited warm rinse function, the manual actually does tell you about it, but who reads those things?
From the manual for a Whirlpool Estate model with limited warm rinse:
On models with Warm/Warm temperature selection, the warm
wash will be followed by an energy saving cold rinse followed
by warm spray rinses. This saves energy while providing the
same rinse performance
From the manual for a Whirlpool Estate model with limited warm rinse:
On models with Warm/Warm temperature selection, the warm
wash will be followed by an energy saving cold rinse followed
by warm spray rinses. This saves energy while providing the
same rinse performance