Unblockable Wording

On one card it says "invisible stalker is unblockable" and on the new card announced it's says "triton shorestalker can't be block". Why have a difference and couldn't unblockable be a key word like indestructible became a key word?

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We looked into making unblockable a keyword but we have enough variance in how we use it that it wouldn’t work as a keyword, so we changed how we worded it to stop making people feel like it was a keyword.