VOA has to know that
RHC is broadcasting to NAm during that time. Is this a deliberate
attempt by the US govt to jam RHC during a popular time for listening?

Well, we could also surmise that RHC has to know that VOA/BBC is
broadcasting to Central America during this time. So perhaps it's a
deliberate attempt by the Cuban government to jam BBC during a popular
time for listening.

Of course, there is yet a third explanation. I suspect that BBC is
difficult to hear near RHC's transmitters on a receiver without fairly
good selectivity, just as RHC is difficult to hear near Delano on a
receiver without fairly good selectivity. But as an intentional
jamming technique, broadcasting an AM signal 5 KHz away from the
station you're jamming isn't very cost effective. So the simpler
explanation is that both broadcasters are doing their best to be heard
on a fairly crowded band.