So, a little checking around Anime News Network, and I find out that the director of the third Tenchi OVA series is Kenichi Yatagi, whom directed two big train crashes of OVA series- Macross II (which had a high cheese factor) and the unwatchable Megazone 23 Part III. And, there are very few other credits for him.
And, I wonder...according to the credits, he did co-direct the second Tenchi OVA series. So, he had to have at least a passing familiarity with the plot, in theory.
Then he promptly nerfs one of the biggest character-building points of the first OVA series-in episode 4, when Ryouko can project herself out to a limited extent outside of her cave prison/trap. There's a montage scene of when Ryouko can watch and see Tenchi-and shares in his joy when he sees somebody that's his mother (or at least that's what the subtitle dialog and dub says) play with him.
And tries to comfort him, by the faintest of touch, when Tenchi cries in the rain at his mother's death.
By making the woman seen in Ep. 4 his sister, not his mother, it takes the edge off of the emotions. And, it turns a poignant scene into another case of misunderstanding.
And, it makes Tenchi into another harem anime trope-the "forgotten promise".
Ugh. I'm getting a battleship and bombarding the studio from orbit. Just to be sure. And, there isn't a plot resolution...which means that they're trying to add more story to the series.
I think this is why I liked Tenchi Universe-it ended. And, there was an eventual victor in it.
EDIT-I think I figured out where the "Mom" comment came in, if the dialog is supposed to suggest the sister. After FFing through maybe the last remaining VHS copy of the Nexus fansub of Tenchi (GOD, we used to have to do that to find stuff, didn't we?), and watching the DVD again, I can see where "sis" became "mom". Older-looking woman, a kid of about four or five and still kind of getting the hang of the language...later on, bit older kid cries his eyes out for his mother. The translator probably thought that Tenchi was doing Relationship Spoonerism, confusing "sis" for "mom", and backed it up on the context of the images.
And, damn it, I like this one better than "Oh, it's her sister and Tenchi pulled a Mihoshi..."