1 .他五年前就退休了 = It was five years ago when he retired.
2. 他退休了五年了=
I believe in your own mother tongue, you would level on some words if the order of words changes. So is Chinese.
For native speakers of Chinese, in the dialogue, a few people would pay attention to the emphasis of the some words. I would say mostly it is the personal habit about how to construct a sentence. For the senteces you posted, it might be the speakers try to level on some words; and it could be just a personal habit to say it, and the speaker might not even be conscious what s/he emphasizes on, therefore. That is why context, and source are so important.
2. 他退休了五年了
他退体五年了。 (without the first 了 =He has retired since five years ago.
Or
他退休了,五年了。He has retired. (It has been) Five years. Very colloquial
PS. I don't try to argue with anyone, but share my own input. discuss or share =/= argue.