So by that logic, if He-Man throws his sword, he should immediately become depowered too and turn into Adam once the sword leaves his grip. (That doesn't happen.)
The 200X show doesn't count in Revelation. It's not the same continuityAnd yeah even in the 200X show, several other people held the sword - Clawful, of all people, held it once! Yet I doubt if he yelled the magic words, he would have turned into He-Crab, the strongest crustacean in Eternia. :P The sword always only worked for the chosen champion.
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That's just an assumption though. The Filmation episode "Evil Seed" explained to us that the power of Grayskull even makes Skeletor more powerful, he becomes more powerful just by being in Castle Grayskull. So that's a clear indication that the power of Grayskull doesn't select worthy or unworthy to empower. And good thing Skeletor never knew for all those years He-Man was a result of a transformation of Adam, nor knew the significance of the power sword and saying those magical words "By the Power of Grayskull"!
Speaking of those magical words, we saw in "Teela's Triumph" Sorceress, He-Man and Battle Cat all touch each other as He-Man raised the sword, all saying "by the power of Grayskull" to get back home. So all three of them called on the power.