What the issue would be if it were plumber's tape holding up conduit? After all, plumber's tape is used to hold up cast iron pipe that is very heavy, and may be full of water to boot, so it certainly provides adequate support. Is it just that it's not listed to support electrical conduit? If so, where exactly do you draw the line?--the rafters aren't listed to support electrical conduit, either.
Conduit is listed for electrical use. The building's structure is not listed. Somewhere along the way between the two you transition from listed to non-listed items.
