Update: Some egg on my face here as minutes after posting this I discovered there is an asteroid named '1197 Rhodesia' in the asteroid belt, "discovered by South African astronomer Cyril Jackson at the Union Observatory in Johannesburg" and named after the state. I can see why this could have more easily ended up in the game as the planet name list clearly uses the names of a lot of real-world planetary bodies. However, given my arguments below I would invite the developers to consider how black and African players feel about the game at times necessitating you to "colonise Rhodesia" and make the change to rectify this.
Note: this is clearly a very minor issue and fix which probably doesn't merit a post this long, but living in the post-Gamergate era it is useful to be equipped with the facts just in case this provokes a firestorm of online gamer rage.

I don't want to speculate as to why 'Rhodesia' is in the list of names assigned randomly to planets in Sins of a Solar Empire (and carried into the current Sins 2 alpha because a lot of the content is copy and pasted at this early stage), unless there is some deep lore I am unfamiliar with where Space Cecil Rhodes is a figure in the TEC who colonises a planet where a minority 6% of white people rule over a black majority, I can't quite see how this adds to the worldbuilding of the game!
I have to say it does take me out of the experience of playing one of the finest 4X strategy games ever made when I have to "colonise Rhodesia".
I'm happy to give the developer(s) responsible benefit of the doubt and assume it was used without any understanding of the history of the white supremacist colony which existed as a white minority-ruled holdover of the British Empire from 1965-1979. That they didn't know the history of Rhodesia where in 1976 Amnesty International voiced its concerns about Ian Smith's government imprisoning African political dissidents without trial, torturing them, and for those who were released confining them to "protected villages".
The original game being released in 2008 they could of course not have known that in 2015 white supremacist Dylann Roof would murder 9 black people in a church in South Carolina, USA and that before this his online manifesto was posted to a website called The Last Rhodesian with a photo of Roof wearing a jacket sporting the Rhodesian flag. Although, romanticisation of Rhodesia has been prominent in white supremacist propaganda before and, more intensely, following 2015.
This is a game I've loved massively since I played it as a kid and playing the Sins II alpha fills me with so much nostalgia and excitement for the upcoming sequel. That is why I say, even if we were to put the history of Rhodesia aside (note: I am not saying that we should put the history of Rhodesia aside), the name just looks weird. It doesn't fit in with all the other names there which are mainly derived from science and mythology and it sticks out like a sore thumb, which might lead someone to speculate as to why it was included in the first place!
Above all, let's try to remember that futuristic science fiction settings such as SOASE and Star Trek are loved by so many in part because, despite what new challenges present themselves, they depict a future where humanity finally gets its act together as a species and war, racism and slavery are a distant memory:
The Trader Worlds enjoyed a golden era of lucrative trade and relative peace under the strict guidelines of the interplanetary Trade Order. They had forgotten their ancient history of war and replaced it with a future of endless prosperity.
https://www.sinsofasolarempire2.com/lore