Why don't we have all the old Siri voices after the release of iOS 11?

Hello friends! Anyone who likes old Disney animations will understand this one, lol!

Well: everyone knows that, with the launch of iOS 11, new Siri voices came to replace those used before iOS 10. These, however, did not disappear, at least in theory, they remained with new names, as can be seen in this excerpt taken from a post on the Applevis blog, written by Scott Davert, explaining the changes in terms of accessibility to the new system.

"Assigning The Old New Names
I wrote above that Siri has new voices. However, if you have enjoyed using some of the old Siri voices with VoiceOver, you'll be happy to know that these are still around, but they now have names. The old American Siri voices are now named Aaron and Nicky, the British voices are known as Arthur and Martha, and the Australian voices are known as Catherine and Gordon. These TTS engines are available for download along with the rest of the voices that were introduced in iOS 10."

However, I only find the Nicky voice available for download and use. So where are the other voices that should appear? Did Apple choose to keep just the first voice?

I hope someone can explain what happened to me.

Big hug to everyone, from Ricardo Brandão...