That's how it worked in 6th, but because Infiltrate stated that it conferred to the unit people refused to believe that was how it worked because, well, it almost but not quite said that was how it worked. What does it say about an IC that has Infiltrate joining a non-Infiltrate unit?Pp 167. If one model has infiltrate, all in the unit have Infiltrate. But Infiltrators are deployed after all other units.
Reserves, Pp 135, are declared during deployment. Ipso Facto, they are declared before Infiltrators are deployed.
IC cannot therefore confer Infiltrate onto a unit without Infiltrate at the point of deployment.