The first question is not weird. Because there is a situation when someone applying for a study permit or PGWP and he also applies the OWP for his spouse at the same time. In this case, they might have to fill up 2 forms and use two options."Schedule 1 - Application for a Temporary Resident Visa Made Outside Canada (IMM 5257)" why is this important first question on the application itself is weird. May be I haven't understood what the form is for. Why does they ask are you the principal applicant or the spouse?
Obviously it would be the principal applicant(my spouse) right ? why will I apply for the temp residence if I already have one?
In your case, only applying for your spouse OWP, she will be the principal applicant.