Comment 1 for bug 457053

From TRACE docstring:

       :PRINT Form
       :PRINT-AFTER Form
       :PRINT-ALL Form
           In addition to the usual printout, the result of evaluating Form is
           printed at the start of the function, at the end of the function, or
           both, according to the respective option. Multiple print options cause
           multiple values to be printed.

So, this behaviour is by design as far as I can tell. (If there are good use-case for handling multiple values, please file a new bug describing the desired functionality.)