Just how strong is He-Man?
Some episodes depict him doing feats of strength that would put him in Superman's category.
Others depict him as being only as strong as Captain America would be.
You answered your own question my friend.
He was exactly as strong as the writers wanted him to be for any given episode. And that changes from one episode to another. There is no single answer that can be accurately applied to the whole series.
Yeah, I'm sure they kept those parameters a bit fluid and malleable in order to serve the story at hand.
I know every series has a "series bible" that outlines the characters, the world et. so that the writers have a fixed reference point that helps to keep the fictional universe in some sort of continuity, but that's likely trumped in a show like this by doing what's best for that particular episode, as Navaros said.
Today, where these things are (supposedly) a tad more sophisticated, I'm sure more attention might be paid to such things.
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A journey into the realm of the obscure: http://saturdayshowcase.blogspot.com/