https://www.cbsa-asfc.gc.ca/contact/bis-sif-eng.html
contact them via phone. I have asked them the same question via email but they responded (response attached below) with a general answer and did not specify anything.
My Email
Dear Canada Border Services Officer
I have applied for a study visa for January intake at "UNI TITLE" which is included in the list of DLIs with approved COVID-19 readiness plans. I am preparing to enter Canada given that my study permit is approved. I have learned from unofficial sources that students currently enrolled in January intake can only arrive in Canada 3 weeks before classes start. Can you please confirm if this statement is true so that I can plan my quarantine arrangements accordingly?
Sincerely
My Name
(Their Response)
The Canada Border Services Agency (CBSA) “Contact Us” is available for the public to ask general questions about the programs and services offered by the CBSA. For privacy and security reasons, the CBSA does not answer e-mails regarding personal or business customs cases, immigration-related situations, or third party requests. Information is provided in a general context only.
All decisions with regards to entry into Canada and exemptions to mandatory quarantine ultimately rest with the CBSA Border Services Officer (BSO) at the port of entry. This service does not provide decisions on persons entering Canada.
Please refer to the special measures to help study permit holders affected by COVID-19.
Note that there are several factors that BSOs must take into account before determining whether a person is admissible into Canada, and each person will be dealt with in person on a case-by-case basis. The burden of proof rests with the foreign national seeking entry to Canada to satisfy the BSO they are admissible in accordance with the Immigration and Refugee Protection Act and Regulations. In general a person must have in their possession appropriate travel documents and be personally admissible into Canada and support the validity of their activity.
The current COVID-19 Emergency Orders in Council (OIC) are available on the Government of Canada website. Additional information may be found on the travel restrictions, exemptions and advice section.
Thank you,
Canada Border Services Agency / Agence des services frontaliers du Canada
Ottawa, Ontario
Canada
K1A 0L8