Although my husband is not an Eastern Rite Catholic, where this is a common practice at baptism (and it is called "Chrismation" not confirmation), it was common in the country in which he was born and grew up.  You will find a wide range of ages for most sacraments among the world's nations.

It is unfortunate that there is no real agreed upon idea of what confirmation is supposed to be...that leads to a wide variation of ages of reception/administration and required preparation (if any).