When it says “three backups” it should probably say “three copies.” That would be the master copy, a backup, and an offsite backup. That said, if you had a master copy the three backups that would be bad.
Regarding the two media types, this is a phrase that goes back decades, when were were using Syquest disks, CDRs, or DVD-R media as a secondary backup. The technology has changed and I think hard drives are the only viable option these days and I wouldn’t rely on optical media. Some reinterpret “two media” to mean two different manufacturers of hard drive, spinning drive vs SSD, or hard drive vs cloud backup.
I use a cloud service for offsite backup, but I also keep an offsite copy on hard drives. It’s cheap and easy, and with a bit of discipline you have a fast recovery option under your control.