This is now managed with the status transition in inc_valid_trans.htmpl form.
You may want to have a look there to modify as needed.
check for the preSaveTrigger function and the the lines below:
if(new_code && old_code && new_code === old_code){
show_response(msgtext("New_Status_needs_to_be_different"));
return false;
}
That say new release come with new features (I think this is the purpose ), client must be trained to use those vs. trying to do a step back re-implementing old behavior
my 2 cents
/J