You're correct, in the early concept art it clearly looks like a spacesuit. Where you're not correct is how it relates to everyone else who worked on the movie and what they intended. They wanted it to be a skeleton, he redrew it per their directions.
QuoteIf those spacesuited figures are not the space jockey, then what are they?
Narratively they're the same, but that doesn't mean that they're literally the same entity and that all the qualities of one carry over to the other. They share visual similarities because that's Giger's style, and it's a revision of Giger's earlier concept art.
You should have stopped back when you were saying "it's both a skeleton and a spacesuit" because that was about as correct as you'd gotten so far, although I'm starting to wonder if you understood
why you were correct. Even a stopped clock is right twice a day, after all.