I briefly glanced at LinkedIn's apprenticeship program (linked in the article). It's 6 months. There's probably some sort of legal/HR benefit where if the apprentice doesn't work out, LinkedIn can cut ties.
Is that a negative? Seems like if you're the candidate and you don't work out after 6 months, you wouldn't have to claim you were fired. You can just say you completed the apprenticeship and decided to move on.