Having done the training “RCIA - Beginnings and Beyond” I came to realize that RCIA is often talked about as a specific way of teaching the faith. It’s not quite that simple or hard line.
RCIA presumes specific rituals at specific times during the process of conversion. The instructions, on the other hand, can be done individually, in a class setting, one-on-one with the priest or a catechist, etc. Each parish does what it needs to do depending on its resources and number of converts.
In our parish the one true convert we had was a child of 10 who met one-on-one with a catechist for over a year. She did all the rites that go with RCIA and was finally baptized at the Easter Vigil.
The Anglican spouse of a parishioner was received into full communion after a short period of study with a catechist. She had been coming to Mass for years with her husband.