How can we set aside the significance of Easter from the question of the initiation of catechumens? Catechumens are unbaptized and so receive baptism as part of their sacramental initiation. Baptism is the sacramental birth from death to new life, made possible by Christ’s triumph over death at the Resurrection on the first Easter. Easter is a favored time to hold baptisms for precisely that reason.
Baptisms need not be deferred until Easter though. They can occur on any day, particularly when a deferral to Easter would be imprudent.