You can't say that you are putting a resistance in parallel with something, and then say that it cannot have any effect on it.
If you fit a local earth electrode and strap it to the DNO's PEN via the MET - then it will have an effect on neutral-earth voltage. Under normal circumstances it'll be a negligible effect as there should be very little N-E voltage present. But should there be a broken PEN core, then the combination of the loads on the 3 phases downstream of the break and the resistances of any other parallel earth paths will determine the N-E voltage in the system.
If the loads are relatively well balanced and/or the earth resistances low then the N-E voltage will be low. If the loads are very imbalanced and/or the earth resistances high, then the N-E voltage will be correspondingly high.
Obviously, from a user safety PoV it would be best if every property had a low impedance load earth electrode, and thus in combination having a fairly hard N-E link regardless of where any PEN break is located. Retrofitting these would, as has been pointed out when it was mooted as a new reg, be difficult and/or costly for many properties as a retrofit - but I would have thought a fairly easy and inexpensive thing to do for new builds (drop some rebar, or copper tape, in the foundations and connect to that).