CIC is very unpredictable but yes these verifications happens after medical only,
http://www.canadavisa.com/canada-immigration-discussion-board/pakistan-medical-in-september-2013waiting-for-visa-join-here-t169881.0.html;msg2664499#msg2664499
I have no Idea why they ask for consultant, If they dont have applied via consultant they simply say no, If they did then say yes, maybe CIC has some consultants in their blacklist, so thats not a good sign, since CIC is implementing new rules from June 2014, they want to make sure that only genuine students should enter Canada,