[plt-scheme] Delay/force printing behavior in advanced student language

Compare the printing behavior of delays in student languages versus
the module language by executing the following code:

(define a (delay 2))
(force a)
a

In the module language:
#<promise!2>

In the advanced student language:
(delay ...)

Note that the way it prints in module language gives you information
about the contents of the promise once it has been forced.
It seems like the advanced student language should give at least as
good information as the module language.
Therefore, I would like to see it print as:
(delay ...) before it is forced and
(delay 2) once it has been forced.

Any particular reason it doesn't do this?