My inexpert, layman's understanding is that the answer is Yes, EBRT
can exacerbate hemorrhoid problems.

I had a proctoscopy procedure one year after the end of my
radiation treatment (HDR brachytherapy plus EBRT).  The oncologist
who did the procedure showed me what he was viewing on the
video monitor.  The walls of the rectum looked scarred
by the radiation, with the scarring disappearing as the sensor
moved up, further from the area of radiation.  He told me that
this was normal, expected, and permanent.

Help is available.  The first thing to do, I think, is to make
heavy use of over the counter preparations like Preparation H,
Anusol, etc.  They are different, so he can't just try one, decide
it's not helping, and give up.  My own experience is that the
thick, greasy ones like Preparation H seem to work the best.

If regular use of those fails, then there are prescription creams
and suppositories available with cortisone or other medications
that might work.

If that fails there _may_ be surgical procedures - though I'd only
try one if I was really miserable since surgery always seems to
me to be a crapshoot (which is one reason I had radiation instead
but, unfortunately, radiation is also a crapshoot.  It's a crapshoot
all around.)

   Alan

Yes!  EBRT can cause and, more often, exacerbate hemorrhoids.

My hemorrhoids were exacerbated during EBRT and my doc gave me proctasol,
but told me they won't heal until well after the treatment.  He was right.