The only outrage I remember was when Rhode Island was blocking people who lived in New York (and only New York - they didn't even care about people from their own state who were in New York; keep in mind that, by that point, the virus was already in many places that were not New York). Rhode Island never actually dropped quarantine requirements, but they did eventually change them to something that made more sense. So the reason for the outrage wasn't that they were asking some people to quarantine upon arrival - it was specifically who they were (and were not) imposing that requirement on.
It makes sense that there are some restrictions, but those restrictions need to be based on actual things that could help curb the virus, not security theater to make people "feel" safe. The virus does not care where you live or if you have filled out a form. Someone who has quarantined in New Brunswick for two weeks is effectively no different from someone who actually lives in New Brunswick, so why should they be treated differently? There is no reason they can't have people on the NB/QC border and at the airports collecting information on all travelers coming from outside (something like "John Doe, born on [date], [insert picture here], from [address], entered on [date] in a [make/model/color car] with a licence plate of [whatever] (or is renting a car, etc.) and is required to quarantine until [date]. They will be quarantining at [address]"), share that information will all other provinces, and then have licence plate readers and facial recognition cameras at the border. If the traveler is detected, a police officer stationed at the interior provincial border pulls them over, slaps them with a huge fine (I believe NY's is $10000), and does whatever they do to force them back into quarantine (you want draconian? Throw them into solitary confinement for two weeks from the date of offence, that will teach people not to break quarantine!).
Honestly, if people are clamoring to shut down borders between provinces over three people who arrived from out of the country and are presumably in quarantine and not a threat to anyone, it seem a lot like panic to me.
In short - yes to reasonable restrictions that actually help prevent the spread of the virus, no to security theater.