Now when I check, both problems have gone away. I haven’t rebooted my phone so I’m not sure why it is corrected now.
Zoom stats now appear and app is blocked. It was a small amount of data, less than 10KB, so perhaps there was a small timing difference in the sample period between Android and GlassWire. But I’ve no idea about the firewall issue. Anyway, I can’t check either now but will check to see if either issue returns.
FYI, I know that there wasn’t a problem before this because when another user said GlassWire wasn’t recording data usage accurately I compared the Android per app usage. It was all near enough and all the apps I used were there. The only notable differences were that Android system activities were recorded differently under different process names and even aggregated:
Since then I installed Skype, Zoom, Whatsapp, and Messenger (replacing Messenger Lite) for video conferencing during COVID19 isolation. I just checked for data usage and all four appear correctly.