If you replace "不十分" with "不太", the whole sentence will be much better, we rarely use "不十分". Consider below sentences:
Grammatically both are correct, but we usually say "B"
Sorry a bit off topic, here's the answer to your question:
他不十分滿 is incorrect?
"不滿" is a feeling. It means not satisfied, but if you use "他不十分滿", the word "滿" will be another meaning, "滿"means full, the whole sentence's meaning will be:
He's not very full (not very full here doesn't mean he's hungry). It doesn't make any sence.
他不十分滿意 is correct?
"滿意" is a feeling, it means satisfied, so if you add "不十分"in the front, the meaning will be "he's not satisfied".
So to conclude,
滿 are two different words and have different meanings.