I think this is the key point, that the landlord can check to see if anything looks molested and then get a proper inspection if there are any doubts.It is possible for tenants to meddle with the electrics, but generally tenancy agreements prohibit this, and anyway it would become apparent with the periodic inspections that landlords make during the tenancy.
I suspect it is far more likely that a tenant would fiddle with electrics than gas! But also more likely it is simple damage to accessories.