Was pre-X Mac OS similarly newline-agnostic, or did it only regard CR
as a line separator?
IIRC, the same results were returned pre-Mac OS X for text objects;
certainly that was the case in Mac OS 9. (I believe that, before
AppleScript 1.9.1 / Mac OS X version 10.2.3, Unicode text objects
only regarded return and the Unicode paragraph-separator character
as paragraph breaks.)
"String" objects have been line-ending-agnostic since AppleScript
1.5.5 (which shipped in Mac OS 9 or 9.1); kai is correct about Unicode
text except that the change was in 10.2.0.