When I first opened the drawing it didnt' stretch. I went into block editor, made sure wipeout frames were on and re-added the wipeout and polyline to the stretch parameter. Saved the block and it worked like it was supposed to. Recreated the steps with the original download drawing and it worked again after editing the block. Reinserted the block in the drawing and it worked, too.
So, it sounds like one of the benefits of the "Suite" approach to design software is new bugs from unanticipated interactions between the applications. Pay more, break more?