With the lower extremity "function" is inherently bilateral. That is, because the primary function of the lower extremities is ambulation, bilaterality is inherent.
(By "advantage" I do not suggest that I buy into the concept that the lower extremities come back before the upper extremities post-stroke. This is common wisdom in rehab, but it may be incorrect. The only way to prove the lower extremity comes back before the upper extremity would be to measure the most distal element of both: the fingers and toes. Measuring toe extension in comparison to finger extension has, to my knowledge, never been done.)
Beyond bilaterality, ambulation is also inherently rhythmic. The rhythm after stroke is disrupted and made unequal. And rhythm is what bilateral leg training with rhythmic auditory cueing attempts to re-establish in the lower extremity.
That is, if you re-establish the rhythm of gait, you will go a long way to re-establish symmetry of both step length and step timing.
There are commercial systems that use a heel switch so that the moment of heel strike is radio-delivered to headphones. The patient hears their own heel strike through the headphones, as well as a beat that they have to match with each heel strike.
But as is true with many technologies purported to help stroke survivors relearn movement, no special system is really needed to bring the idea of rhythmicity into gait.
A simple metronome either heard through headphones or carried by the therapist next to the stroke survivor can be used to promote the re-establishment of rhythmicity of gait. Plugging the ears using standard noise-reducing plugs can boost the volume of footfall to make that obvious to the survivor. The trick is then to match the footfall to the beat.