Canada currently has travel restrictions in place due to the COVID-19 pandemic. Travellers who are allowed to enter Canada, such as Canadian citizens and permanent residents, must quarantine for 14 days, unless they are providing essential services.
In the case of a Canadian citizen or other individual who is allowed to enter Canada, and who is currently living outside Canada and would like to visit Canada for non-essential purposes, would it be allowable to visit for less than 14 days (remaining quarantined for the entire period) and then return immediately to where they came from, or would such a visitor essentially be forced to stay in Canada for 14 days from arrival?
I just called the Canadian Gov't with this exact question. I need to enter Canada to pick up a non-essential item (a pet). I am planning on flying from the US to Vancouver, staying overnight and returning the next day. The hotline told me that departing early is absolutely permitted, as long as you exercise quarantine measures at all points while in Canada.
would it be allowable to visit for less than 14 days (remaining quarantined for the entire period) and then return immediately to where they came from [?]
In my (almost) personal experience: yes, it would.
I know someone who is in the opposite situation: a US citizen and a Canadian PR (living in Canada) who has been traveling back and forth across the land border a lot. They have several times spent fewer than 14 days in Canada between trips to the US. In keeping with quarantine, you need to exercise caution (see below) in traveling in both directions between your place of residence/quarantine and the US border.
Discretionary travel includes, but is not limited to, tourism, recreation and entertainment.
If a traveller's entry is permitted, they'll be subject to mandatory quarantine for 14 days.
So it appears that it’s technically allowed to stay 14 days or less (or to be more precise it’s not explicitly forbidden to stay 14 days or less) but who would want to do this? As the Atlantic article linked by @MarkJonhson indicates, and a per anecdotal experience of people I know, there is a follow up by Canadian officials to “make sure” that people respect quarantine when they have to. There are even instances of Americans legally entering Canada fined for sightseeing stops on their way to Alaska.
Now, I imagine that if you plan to stay for less than 14 days, the officials at the border will need quite a bit more convincing about the seriousness of your quarantine plan than if you planned to say for an extended period. They might let you in or they might deny you entry on the grounds that this quarantine plan is not realistic.