Firstly, people briefly walking past your wall shouldn't trigger either system as they're both set up to require a period of time and a certain signal strength.

Firstly, people briefly walking past your wall shouldn't trigger either system as they're both set up to require a period of time and a certain signal strength. Secondly, situations like this are possibly one of the situations that will benefit this NHS-style centralised contact tracing over the distributed one as they can apply more advanced models to the nature of the exposure and try to reduce false positives. Or indeed, potentially expose that information to human contact tracers (though right now they say they have no plans to do this).