I may be misunderstanding what you’re saying but i’m pretty sure Texas has first and second degree murder. This was a second degree conviction just referred to in Texas as murder. As opposed to first degree which is capital murder.
Seco
IOW-you will get charged with murder in Texas if you walk in, find your wife sleeping with another man and you kill them both. In most states thats second degree murder. Not in Texas. Thats just murder. However, In Texas, passion can be argued as a defense at the punishment phase.
So, what happens in Texas is you get a murder charge and a sentence that looks like a CNH or manslaughter conviction due to circumstances.