Inspired in part by discussion on the Anglican Ordinariate thread, it occurs to me that there are two dominant models according to which the Rite of Christian Initiation of Adults is understood and practiced.
In the first — let’s call it the Catechetical Model — the RCIA is primarily a process of catechesis ordered toward the intellectual and/or spiritual development of the participants. In this model, significant developmental milestones are marked ritually by the various ceremonies: the Rite of Welcoming, Rite of Sending/Election, etc.
In the second — let’s call it the Ritual Model — the RCIA is primarily a series of rites leading to Baptism and the function of catechesis is to prepare the catechumens to participate meaningfully in those rites.
In my experience, those who adhere to the Catechetical Model are more likely to see no problem with candidates for full communion and catechumens participating in the same catechetical process and are more likely to favor using the combined rites for candidates and catechumens and even, in some cases, having candidates participate in the scrutinies. After all, if they are going through the same catechesis, they should have the same milestone markers. Those who adhere to the Ritual Model tend to make a sharper distinction between candidates and catechumens, even having separate catechetical tracks where the resources for this are available, and perhaps being a bit looser about the amount of catechetical preparation needed before a baptized Christian participates in the rather minor ritual of reception into full communion.
I don’t think these models are mutually exclusive. In fact, it is probably good for an RCIA “team” to have members who incline toward different models. My own bias is toward the Ritual Model, but for a number of years I co-directed an RCIA program with someone who was much more inclined toward the Catechetical Model. I think we collaborated well and since his sudden death a little over a year ago I feel our program has been impoverished. But I think that one thing that enabled our fruitful collaboration was our awareness that we approached the RCIA differently.
My general sense is that the Catechetical Model has been dominant for the past few decades, but that the Ritual Model has been recently gaining ground. My own diocese has been strongly urging parishes not to initiate baptized Christians at the Easter Vigil but to find another occasion for their reception into the Church. This, it seems to me, reflects a view that the rites have a certain primacy over the catechetical process, so that participation in a common catechetical process should not necessarily imply participation in a common set of rites. It might even entail the view that different rites call for different processes of catechesis.