While I defer to the ERISA attorneys, I'd just observe that it is the participant who wants the distribution that is saying there will be a divorce - what ulterior motive would a participant have for making a statement that serves to delay or prohibit a distribution to himself? So I think it is pretty reasonable for the plan to put a hold on the account based on that, pending whatever additional written confirmation/statements whatever an attorney would tell the plan is appropriate.
I think the "may" is fairly standard language, to allow some Plan Administrator flexibility.
And, good luck getting a statement indicating marital bliss.