大方廣佛華嚴經隨疏演義鈔 9.31

9.31

疏「一、中間三教存三泯二別」者，始終頓三名為中間，以初有小乘、後有圓教，故名中間。而始教存三，故別為一教；終頓二教泯二是同，故為一乘，即合終頓二教也。

Regarding the commentary's "First, the difference of preserving the three and eliminating duality among the intermediate three teachings": the initial, final, and sudden are called "intermediate" because the Hīnayāna is at the beginning and the perfect teaching is at the end, hence they are called "intermediate". Since the initial teaching preserves the three, it is set apart as one teaching; the final and sudden teachings are identical in eliminating duality, so they constitute the one vehicle, which combines the final and sudden teachings.