Bodhicitta (the mind that is bodhi) can be a confusing term. As early as the Samdhinirmocana Sutra, Bodhicitta can either be relative/conventional, which is samvriti-bodhicitta or it can be absolute, which is paramartha-bodhicitta. Samvriti-bodhicitta denotes aspiration as with a vow and actually carrying out the vow. Still, this is not the same as paramartha-bodhicitta. At this point, it starts to get confusing.
More than often I am inclined to suspect that those who have taken the vow of a Bodhisattva assume they have attained paramartha-bodhicitta. However, the aspiration or vow cannot bypass paramartha-bodhicitta which is actually manifesting the Bodhi Mind (bodhicittotpada). With paramartha-bodhicitta one, so to speak, is a baby lion who will grow up to become a big Buddha lion. On the other hand, with samvriti-bodhicitta one is not a baby lion; its more like a dog or a chicken aspiring to be a lion.
We note that in the Brahmacarya chapter of the Avatamsaka Sutra that "at the initial moment of the activation of the bodhicitta [utpada], full enlightenment is attained." Obviously, this is paramartha-bodhicitta and not samvriti-bodhicitta. When Zen master Shen-hui is talking about Bodhicitta in this passage it seems that he has in mind the conventional or samvriti-bodhicitta.
Since you have already come to this ordination platform to study the perfection of wisdom, I want each and every one of you to generate the unsurpassable bodhicitta both mentally and orally and to become enlightened to the cardinal meaning of the middle way in this very place! (Seeing through Zen by John R. McRae, p. 55–56).
It is hard to imagine that new ordinands will suddenly achieve highest Bodhicitta even with a rousing sermon by Shen-hui. From this we might even surmise that in the early formation of Zen teachers, like Shen-hui, confused Bodhicitta for sudden enlightenment. In any event, it is not difficult to confuse samvriti-bodhicitta with paramartha-bodhicitta. But this was not always the case. Nagarjuna explains it quite nicely in this passage from his Bodhicittavivarna.
When a Bodhisattva, having practiced a course by way of mantras, has thus produced the bodhicitta that in its relative aspect has the nature of aspiration, he must by means of meditational development produce the absolute bodhicitta.