This is 100% wrong and makes zero sense. Your friend doesn't know what he's doing and clearly doesn't understand basic Canadian immigration rules and processes. Don't listen to anything else he says. He should not be working as an immigration consultant if this is the kind of advice he is providing. Honestly, this is just so so so wrong.
You absolutely can do Family Sponsorship with your son physically in Canada (as long as at least one of the parents is living in Canada when the application is submitted and continues living in Canada while the application is processed). This is the RIGHT way to sponsor your son. Withdraw the H&C application asap. This is the wrong program. There are no barriers to you sponsoring your son and the H&C application will take much much longer than a regular Family Sponsorship application. Submit a new application under regular Family Sponsorship. There are tons of people in the Family Sponsorship section of the forum that are sponsording dependent children right now (just like your situation) with the child in Canada. Go to that section of the forum and look for threads on dependent child sponsorship.
I cannot believe you got such wrong and horrible advice. Your friend is an idiot who shouldn't be working in this field. If his applications are being rejected, they are being rejected for other reasons. Probably because he sucks as an immigration consultant.
EDIT: Here's one of the threads dealing with dependent child sponsorship in the Family Sponsorship section of the forum:
https://www.canadavisa.com/canada-i...ependent-child-sponsorship-2022.779244/page-3