cstanley,
I certainly am not a Shito-ryu expert, though I know a few on the nets. In fact in my 35+ years I've never met one. Not surprising as arts tend to hang in pockets around the world.
My looking at Shito-ryu always began with Mabuni Kenwa. I even translated a french version of his orignal two books from 1933/34 to understand his initial contributions.
The texts in my library discussing Shito Ryu kata don't have mentino of Ten No Kata.
So I've used an inadequate tool of Google search to look at Shito Ryu kata.
Here is what I see on the quick.
First searching for Shito Ryu kata lists, I find the 'standard' Shito Ryu Kata lists with no Ten No Kata listed:
http://www.genbu-kai.com/katalist.html
http://acpcommunity.acp.edu/facultystaff/moon/Karate/Katalist.htm
http://www.mudgala.com/karate/shito_kata.pdf
http://www.shuriway.co.uk/kata.html
http://tanutech.com/japan/kata.html#Kata Page
Then seraching for Shito Ryu Ten No Kaat I find some Shito Ryu Kata lists with Ten No Kata
http://www.azbudokan.com/Shitoryu Assoc.htm
http://employees.oneonta.edu/davisgb/karate/kata.html
http://ahealthybodymassage.bizland.com/karate1.html
All of which are difficult to decypher. But then I find a Shito Ryu list with Ten No kata and it states: Under Kata of Shito-Ryu: Ten no kata:Kata of the Heavens. A kata of Funakoshi Sensei similar to the basic Fukyu katas of Okinawa.
found here:
http://www.angelfire.com/sk/budokai/Katainfo.html
So the issue is one of knowing which sources are the 'right ones'? And not being inside Shito Ryu it's a distinction hard to make.
But it does confirm that there are Shito Ryu groups using the name Ten No Kata, but apparently with different practices in that name than what you practice.
It is a complex world.
Now as to why someone renames the kata, beyond me. It appears Motobu Kenwa didn't do it. On the other hand Funakoshi Ginchin did it, publically expained in his writing.
Why someone renames one kata with a different name, have to be honest, hardly seems worth the effort to my way of thinking. But to each their own. I still maintain all this makes meaningful open discussion very difficult, especially if one throws a name out there and doesn't provide the context. But apparently there is a lot of diversity within the name Shito ryu. Not an uncommon problem in most systems including my own.
As for Funakoshi, I respectfully disagree that he created a mess. One of the absolute best karate-ka I've trained with is a Shotokan practitioner whose father trained at the Naval Academy in the 30's. But then the Shotokan he practices does not match the descriptions of other Shotokan groups in the least.
Perhaps the question about Funakoshi's art has nothing to do with Funakoshi....hmmm.