That it does not do.
It provides a greater degree of safety for the simple reason that it trips almost instantaneously. For a circuit breaker to trip because of a ground fault the current flow must exceed the breakers rating. If you happen to be in the circuit that is quite a shock. Note though that the purpose of the two are different. A ground conductor merely diverts the current flow in the case of a mechanical (insulator) failure. Relying on the OCD to work when overload is reached. Depending on the circumstances you could have a fire in the mean time or die from electrocution. A gfci breaks the circuit as soon as it senses an abrupt change in current flow. Essentially it is much faster and will prevent the OCD from ever reaching capacity.
Note also that your report of knob and tube will need to state if that wiring is live (in use). Many older homes still have knob and tube in the attics or cellar that is not hooked up to anything.
The rate that insurance companies are no longer writing new policies in entire states, it’s only a matter of time before every company is going to follow with the K&T. The same thing with galvanized water piping & Stab-Lok panels. We have had a couple of derechos here in the past few years so I can envision 4-point inspections being required in new states as well.
A GFCI receptacle will work without a ground wire attached and can be tested on the device face but not on an external testing device.