Yes, but I wonder if there is a rock-solid guarantee that each array
that is an element of idsAndJellyBeans is in fact from the same "plan"
record.

Empirical research suggests that they are, but I'm nervous.  That's why
I wonder if there is some sort of pure-REXML trick that would extract
multiple elements from within a single record, so that I could always
be sure that the id and the jellyBean in each individual array had FER
SHURE come from the same "plan" record.