They may be, but even attendings in other specialties aren't 100% about staging. I'm sure I'm not 100% either. Better to review imaging and make TNM staging decision yourself. For rectal cancer it's hard to have a very accurate T stage unless there's been an endorectal ultrasound or at least MRI of the pelvis.
For the rectal cancer PDF, go to page 3. All of the blue links (I'm assuming you're using it on a computer as a PDF rather than a printed out version) can be clicked on to take you to them. Click on 'Staging (ST-1)' which takes you to page 45, which has the details on the TNM staging classification for rectal cancer. This page is what I am talking about in determining the patient's stage, as much as you can, with the information at hand.
Page 11 is the staging work-up necessary for a patient with biopsied rectal cancer.
There is a difference between knowing the stage for a patient (what their TNM stage is) versus knowing how to stage them (what exams do you get to figure out what their TNM staging is)
Most of the time, if you're meeting a patient that was referred from another oncologist, they have already gone through most of the appropriate staging work-up (although sometimes it isn't ordered or is pending). If they haven't (as outlined on page 11), that would be the first step (to finish what was necessary) prior to recommending treatment.
My recommendation was that you at least know the TNM stage of the patient (as much as possible), similar to knowing all of page 45 from the rectal Ca pdf. The next step up is knowing what staging exams should be done for patients with this diagnosis (Page 11). The next step up is knowing what the treatment should be for that patient, based on the stage of disease they are (follow the guidelines for the stage of disease mentioned).