Would my grounding conductor be “choked” out by metallic conduit?
You want Schedule 80 PVC, not a metal rigid conduit

Assuming that the engineers want the grounding electrode conductor protected from physical damage, then the tool of choice for this job is Schedule 80 PVC conduit, as you are correct that putting a single conductor in a ferrous (steel) conduit will cause a "choke" effect that impairs the ability of that conductor to carry current.  Either that, or if ferrous conduit is required, then use a conduit grounding clamp, jumper, and lay-in tap lug at each end to bond the conduit to the conductor -- this suppresses the choke effect.