chakrab said:
but seriously, CIC doesn't mandate inland applicants to stay in canada. just that they should be available at the landing interview.
Completely wrong. They indeed mandate it.
http://www.cic.gc.ca/english/resources/manuals/ip/ip02-eng.pdf
CPC advises sponsor that applicant is not a member of the family class if they are not cohabiting with the sponsor in Canada
http://www.cic.gc.ca/english/resources/manuals/ip/ip08-eng.pdf
Cohabitation - One of the eligibility criteria in R124 is cohabitation with the sponsor in Canada. Documents provided as proof of the relationship should also establish that the spouse or common-law partner and the sponsor are living together. If this is not clear from the evidence available, the CPC-V should request further documents or refer to a CIC for an interview
Each time you cross the border there are records of it. So if CIC wanted to check, they can see if anyone is currently in the US or Canada, and for how long. To risk this is not advisable as who knows when CIC may feel the need to check up on this.
And even when an inland applicant has PR approved, at the landing interview it's common for the CIC officer to ask for proof of cohabitation in Canada. There's been a few cases here of inland applicants being rejected for PR at their landing interview when the officer finds they actually weren't cohabiting.