2005 was when wording changed to like it has been ever since then.
2002 250.50:
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2020 250.50:
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I didn't copy 2005 simply because it started bottom of page and ended on top right, but is word for word the same except references to 250.52 did not go to (A)(8) in 2005.
At the time they first changed this they had discovered because of the previous wording "if available" usually ended up turning into electricians showing up after concrete was done and since the CEE wasn't really "available" people weren't using it.
The exception for existing that was added basically allows you to change or upgrade a service in an existing building that didn't have a connection to a CEE to not have to disturb concrete to make it accessible. New construction however has no exceptions to not use the CEE if a qualifying CEE is present.