they are considered to be on the earth-facing surface...
Actually, an "earth facing" antenna can be confusing to some.
Roger that. A narrow-beamwidth directly under ISS would not serve well. I was (in)effectively paraphrasing the cited reports, that observe that the primary antennas are mounted on the (earth-facing) Nadir side, as opposed to the (space-facing) Zenith side. For a simple single vertical element, pointing directly toward earth gives a good view either side, and front/back. Not so sure what pattern or beamwidth to expect from the patches.
As I read it, both WA1 and WA2 have capability to Tx and Rx at the same time, but "the space station ham shack will install a dual-band, 2 meter/70 cm radio and a 70 cm radio that will use the downward/Earth-facing WA1 and WA2 antennas" I would suspect that the cross-band setup uses one to Rx, and the other to Tx. Which might yield a 'deaf-zone' for each, but not in the same place.
Possibly if we dig around the ARISS info, more detail has been provided. (I see that KA3HDO has just posted some new links...)
Thanks /;^)