Likely not, since he was writing about followers of Jesus during Jesus’ own lifetime, before there was such a thing as the Catechumenate. (He was actually writing for the Catechumens of his own time, though, and he was certainly aware of the Catechumenate.)
Keep in mind that Jesus’ disciples were all baptized by John for repentance from sin prior to joining His group.
Discipleship is following Christ’s commandments. One of them is you need to be baptized to inherit eternal life. So maybe if one intends to be baptized, they can be considered a disciple, but not until they come not only to believe but to obey.
I still just like to go with what the simple word “student”. Recall that the word we translate from Matthew (and all the other places it is used) as “disciple” is actually a very common Greek word, “
mathetes”. It was used not only by Jesus and the New Testament writers but by many other people in that day. And its meaning is not derived from its usage in the scripture, but rather its meaning in the scriptures is derived from its usage in everyday parlance. (I.e. the biblical writers might give their own emphasis to a word, but they couldn’t change its basic meaning and still have people understand them.)
And the word we are speaking of goes back in usage to Homer and beyond. It ancient Greek it had to do with the process by which one acquires theoretical knowledge. In Socrates’ day a person was considered a “
mathetes” (or pupil) only when in the presence of his “
didaskalos” (master or teacher). But Socrates never wanted to have any “
mathetes” and didn’t consider himself a “
didaskalos” because he desired those who learned from him, to learn how to think independently of him as well. Thus it was that those who learned from Greek philosphers became known as "
akolouthos (followers) as much as “
mathetes” (students).
By the time of the New Testament, the word “
mathetes” in its most common secular usage simply means “student”. But I think that in reading the New Testament in context that one can see that the writers goes back and pick up on the concept of a “
mathetes” as one who is totally attached to someone as if apprenticing from them how to become like them. This mirrors the relationship between Jewish rabbis and their students.
Now that is obviously a process. One does not become like Jesus just by virtue of being baptized. Rather, in baptism one gets attached to Jesus in both a symbolic and spiritual way, and then grows in grace to become more and more Christ-like.
So, I respectfully disagree that discipleship is as simply as following Christ’s commands or obedience to his word. I think it goes beyond mere behaviors to the spiritual core of an individual. Do we do more than just mimick Christ outwardly, do we actually seek to in some measure ourselves inwardly be transformed into one who carries the image of Christ within his/her own soul. In otherwords, I think that discipleship is ultimately about sanctification and is a life-long process, not a one time happening.
And while you may see that as starting only at the moment of baptism, I see it starting any time a person becomes attached to Jesus – be it through the sacraments or by a simply act of faith and personal commitment. We become students of Jesus and remain so throughout our lifetime. Graduation being our own glorification when we enter into God’s presence in heaven.