I think it is. Jimmy Fusco taught me that a novice should start with the three-ball ghost and shouldn't move up to the four-ball ghost until they've won five sets in a row. Once they've won five sets in a row against the four-ball ghost, they can move up to the five-ball ghost, etc., etc.
This approach to playing the ghost ensures that the ghost is a proper test and good practice at all levels of play.
Is the an agreed upon training etiquette for breaking the lower number ghost racks when you’re doing if for self evaluation? For something like the 5-ball ghost, a soft break keeping all the balls at one end of the table is a substantially easier rack than a full power break.