Not necessarily
One of my friend application returned he did master from pakistan for this reason not language proof.his degree was also in enlish.share the link please, this is what I can read from the guide :
You attended or are currently attending a secondary or post-secondary education program in English or French, either in Canada or abroad, including:
- A degree, diploma, certificate or official transcripts from a secondary or post-secondary education program showing you studied in English or French, in Canada or abroad.
- If the original document is in a different language, include:
- a letter from the school showing that the language of instruction was in English or French along with (including an official translation of the original document, if needed)
- the address and contact information (phone number) of the education institution
If your degree is already in English or French, this already shows that you studied in English or french. You cannot study in Russian and have your degree in English or French. If your degree is not in English or French then you need a letter showing that the language of instruction was in English or French ( see above).
Your point is also valid but may be our countries official language is not English thats why thay required that certificate and for safe side i will personally recommend to get certificate.