An online article from The Star (Toronto ON) confirmed my hazy memory of the release of the 1921 Canada census -- it was available very quickly because of partnership with ancestry.com:
1921 Canadian census data released online, to genealogists’ delight (Fri., Aug. 9, 2013)
The 1921 census was released by Library and Archives Canada on the
Ancestry.ca genealogy site Thursday. ...Library and Archives Canada
has never published the census without a partner. Transcription and
organizing work has already begun at Ancestry.ca, so people can search
by name, location, and other key details, later this year. The raw
data is available for free on the private site already, and according
to Anderson, will also be available on the government site in three
years.
A more detailed timeline is found at
Wikipedia - Canada 1921 Census - Release date and format
...In 2013 the records were opened for public use and transferred to
Library and Archives Canada (LAC). ...On 8 August 2013, raw digital
images of the population schedules were made available to browse for
free with a geographic index of districts and sub-districts on the
private Ancestry.ca website. Ancestry.ca transcribed and indexed the
data to facilitate advanced searches by individual Ancestry.ca
subscribers, and in person at LAC and subscribing libraries, from late
in 2013. The census data was scheduled to be made available on the LAC
website three years after being made available on the Ancestry.ca
website. The fully indexed online census data was launched by
Ancestry.ca on 29 October 2013. The data is free to search, subject to
registration on the Ancestry.ca website. On 30 August 2017, the
results of the 1921 were made available on the Library and Archives
Canada website.
As for the 1926 census, Libraries and Archives Canada says (as of 6 Jun 2018) :
Regarding the 1926 Census of the Prairie Provinces (Manitoba,
Saskatchewan, Alberta), we are currently developing an index and plan
to make the data from the census available on our website; in the
coming months we will be in a better position to estimate a release
date.