As I mentioned above, the Dhyana/Chan lineage is important, even if not "historically accurate" as it gives a clear idea of the position of development of the Chan school from their own perspective- that is in respect to the "Three Turnings of the Wheel".

The first, is the Buddha's early teachings on such topics as the Four Noble Truths of the Arhat-path. The Dhammapada and other texts of the Pali Canon are considered part of "first turning" teachings.

The second, is the Buddha's Mahayana teachings on such topics as emptiness & compassion, which form bodhicitta of the Bodhisattva-path. The Prajnaparamita and other texts of the Madhyamaka school founded by Nagarjuna (14th Dhyana patriarch) focus on these elements and are considered "second turning" teachings.

The third, is the Buddha's teachings on "Buddha-nature", elaborated on mostly by the Yogacara school founded in part by Vasubandhu (21st Dhyana patriarch) and his half-brother Asanga who received teachings from Maitreya on the subject, considered "third turning" teachings.

In other words, the "3 Turnings" views all of the Buddha's teachings as essential at certain stages. One doesn't just come to Mahayana teachings without having first studied Hinayana, some time previously. They'll be too concerned with ending personal suffering and need the 4 Noble Truths, not some talk about "emptiness" and the Bodhisattva-path which will not interest them. In later teachings, the 4 Noble Truths are seen as provisional. They are essential "truths" from the point of view of someone who is clinging to their own suffering as a real product of real circumstances. Once such view is broken, those truths are no longer necessary. Enter Mahayana, begin bodhicitta.

One of the main focal points of Yogacara is the 8 layers of consciousness. This is also a big subject in the Lankavatara Sutra, the only sutra from which Bodhidharma is said to have taught.

So if you study these schools (Yogacara being extremely fine detailed in explanation) you can better understand the Chan school, and those nonsensical Chan sayings make "sense" without getting all "zen".