Perhaps it's the difference between the Theravada motivation and the Mahayana motivation we are talking about here.
From the forum of Lama Shenpen Rinpoche's Dharmaling Congregation:
The difference is mainly in the motivation.
Theravada practitioners will focus on reaching Nirvana, Emptiness, and once reached, will remain in it for eons!
Mahayana practitioners will focus on helping others, wishing to reach omniscience for the sake of the others, reaching Emptiness as a means, not a goal.
It adds some specific practices to transform every moment in practice, transforming the perceptions, the energies directly into the pristine nature of the Buddha practiced.
The Therevada vehicle tends to rely only on Shakyamuni and his teachings whereas the Mahayana way takes into account Bodhisattvas and other Buddhas and their teachings and help.
"If we can attain nondual, nonconceptual awareness in meditation
As our meditation becomes effective, the attitude of others towards us begins to change, and they themselves begin to turn inward and to search with greater conscientiousness through the stuff of their own minds and lives for spiritual solutions to their own problems.
...how the benefits of meditation are not limited soley to the meditator
The later add-ons you refer to are the teachings of widely accepted realized beings or those who are called Bodhisattvas.
It is the Mahayana belief that all beings are in reality seeking happiness and want to be rid of their suffering ...
...and we are Buddhists not just for ourselves alone to transcend suffering...
but because we see it as a vehicle to bring enlightenment to all.
Mahayana Buddhists believe in a dark age when the Buddhist teachings will be lost