Billing codes are purposely complicated to deny legitimate claims a lot of the time. Two nearly identical codes will have one covered and another not for whatever reason they come up with. It’s why there are entire teams to handle billing at large institutions.
The real question honestly, is if those individuals were authorized to give shots, are there different billing codes that should have been used instead? And if not, why?
The Canadian Healthcare system isn’t that different from the US as much as you all might want to think it is. You just have fewer groups paying, the bullshit complexity built into the system is a near copy of the US.