I have now asked my "real" question (one whose answer effectively answers this question) here ("Are getting hit and taking damage simultaneous events").
The shocking grasp spell's description states:
On a hit, the target takes 1d8 lightning damage, and it can't take reactions until the start of its next turn.
It is unclear to me when the reaction prevention actually occurs (on being hit or on taking damage).
I have found this Q/A ("Would Shocking Grasp prevent the target from casting Absorb Elements?") where a comment from @DavidCoffron says:
[shocking grasp] interrupts the damage taking (which is the trigger), not the hit (which causes the reaction-block)
And then there is this Q/A ("Can the Shield spell be used against Shocking Grasp?") where the following sentence exists in @chaoticgeek's answer:
In addition you take damage and can't take reactions together so if you can prevent the first you have to prevent the other since it is a chain linked by 'and' in this situation...
[T]he reaction prevention only comes with the damage that is dealt
Does the 'and' in shocking grasp really link the clauses enough to make them simultaneous? Are the hit and the damage happening at the same time?
Does shocking grasp prevents the target from taking reactions once the spell hits them or once the spell damages them?
I do not believe that this Q/A ("When Shocking Grasp hits, can it trigger Wrath of the Storm reaction?") is a duplicate of mine because I am specifically wondering when you are prevented from taking reactions, which (as the quotes above show) does not seem to be entirely agreed upon.