There has been much debate over this very topic.
While it is true, that an Inland applicant does not need to maintain legal status to APPLY, they DO need legal status to ensure that they are not removed by CBSA (Canada Border Services Agency) before their application is approved. You provided only a portion of what is stated on CIC's website. The next sentence says something like "However, there is no guarantee that they will be allowed to remain in Canada..." It seems like a rather cruel `twist'...stating that a person without status can apply, but not offering that same person any guarantee of not being deported, while they wait...and wait...and wait for their PR decision.
Prior to Jan 17, 2014 a person could submit an Open Work Permit (OWP) with their Inland application and have implied status (provided that they had legal status) that would `cover' them throughout the PR application process. Now that Inland applications are being processed in Mississauga, while OWP applications are still being processed in Vegreville...this has caused quite a number of posts here, questioning how, if at all, this affects implied status.
Have the rules changed? Can an Inland applicant no longer submit an OWP with their Inland Spousal Sponsorship application and be under implied status? NOTHING has been posted to the CIC website to corroborate this `theory' that has been tossed around in these threads. Even calling CIC seems to yield different answers from the phone support. Some say yes, while some say no.
It really shouldn't be this cryptic and since, again, nothing has been posted on their website...it should be business as usual.