Slightly obscure "framer" lossage

[<TIM at MIT-MC>]

In ZWEI in Release 5.1, Experimental MIT 1.4, FEP 18, on Lisp Machine 
Jimi Hendrix (3600):

When an editor line occupies more than one physical line on the screen
(i.e. wraps around) and the cursor is anywhere other than on the first
physical line of that editor line, the redisplayer's framer loses in the
following manner:

For example:  In a buffer that doesn't fit in one window, go to the
middle of the buffer somewhere and type in a very, very long line, then
make sure that the cursor is not on the first physical line of that
editor line and type c-0 x-L.  Where would you expect the cursor to be
now?  On the first line of the screen?  No, the framer lost, and forced
the current editor line to be displayed around the center of the window!