Is it possible for a sorcerer to write all the ritual spells they know in the ritual book of Ritual Caster Feat when they acquire this feat?


I was reading the D&D beyond about wild magic sorcerer and I was thinking about something when I readed the recommended feats, in particular the Ritual Caster Feat:

Is it possible for a sorcerer to write all the ritual spells they know in the ritual book of Ritual Caster Feat when they acquire this feat? Or do they have to found the written version somewhere?

In the feat description, it look like no, but I feel like it doesn’t make sense, since the sorcerer know the spells.