If you have metal siding near the pool/spa it must be bonded along with screen cages, window frames or whatever, just like the ladder.
There was a lot of confusion about this sheet metal screw thing but I think that really only applies to how you fasten a lug or bond wire, not the connection of each piece.
In Florida there are not a lot of "siding" houses, at least not here but you do see it a lot in trailers and they use aluminum gable ends and soffit. The meter pan is as likely to be against block as anything and in a trailer it is in a post.
Again, a while ago, when the Prodigy SS guys were talking a lot I did an experiment and found my Ecos ground tester was happy with the incidental bonding between the gable ends at each end of my house (42') merely by the soffit between them.
The exhaust fan on one end effectively bonded that side and a test from the HVAC service outlet on the other end to the gable showed <1 ohm under load. (the Ecos test parameter)
If you made an effort to connect any metal you penetrated to the circuit you penetrated it with, I think you are good to go. Usually the box is mounted right on that metal (much liker John's meter can example).
I would want to see something more substantial with a pool/spa tho. I do believe if you get one piece, the way aluminum siding snaps together, you have them all.
