Part of the conditions for applying inland is that your spouse must maintain legal status in Canada while they wait for a decision (
source) meaning they do not have implied status. Only certain applications (TRV, Visitor Record, Work and Study Permit extensions) give you implied status while you wait for a decision, Sponsorship/PR isn't one. Since the US is visa exempt, there isn't a visa to extend, hence the visitor record (and if you have a visitor record and a valid travel document, you should be able to leave and reenter canada as long as it's before the end date of the extension, as verified with a CBSA officer last time I crossed back into Canada). I don't actually know if you can get a visa at all due to the US being visa exempt, but I have heard of people being granted a TRV/visitor record at the border in cases like theirs