There is a concern only when the wire is COMPLETELY surrounded by metal. The slightest break in the metal, and there's no concern.
Since most folks use an bare wire for the GEC, I think that concerns over creating a 'choke' effect are greatly exaggerated. Every point where the wire touches metal will break up the 'choke.'
I find it interesting that sparkies always take great pains to bond the GEC at both the panel and the ground rod end of the conduit, yet I always find transformer grounds to be simply run 'free air' out of pipe where they bond to building steel. In addition, transformer GEC's are almost always made using insulated wire. IMO, you've just made a choke point.
I also note a nearly complete lack of appropriate bonding fittings for use at the ends of conduit. Yes, there is that one type of ground rod clamp - a type NOT STOCKED within a hundred miles of me
Yes, there are 'bonding bushings,' but they place the bonding screw in a place that makes you bend the wire back onto the pipe, then reverse it again to continue to your lug on building steel. It's also a wee bit hard to fit larger wires under that tiny screw
Put a ground rod clamp on the end of the pipe and re-assemble it so the part that's supposed to connect to a rod instead grabs the wire? I suppose that might work, but it still looks pretty ungainly.
Would you use a 2-screw romex connector http://www.bptfittings.com/Home/ProductDetail?id=00781747256508
for this use?
All I'm asking for here, manufacturers, is a coupling with a long set screw! Place one end on the pipe, let the other screw pinch the wire. Is that too much to ask for?