The 0.05 relates to the bonding connection, not the conductor length. This is to conform the clamp is connected to the conductive part with a low resistance joint. (i.e. paint removed from pipe). This relates over to the 0.1 + R of lead used in the COP for portable appliance testing, as there are 2 points of connection (0.05+0.05=0.1)
The purpose of the main protective bonding conductor is to equalise the potential, so we only see the volt drop (touch voltage) of the R2 conductor, between conductive parts under fault conditions. If no bonding is present, we will see the volt drop of the R2 conductor, plus the volt drop of the external earth. Obviously this will be greater in TT installations, due to the higher resistance in the earth electrodes.