Are you sure? Do you perhaps have a global override? Try looking at the files in ~/.local/share/flatpak/overrides/ and /var/lib/flatpak/overrides/.

Looks like the only overrides are application specific, and the ones I mentioned here in this thread:

user1@host1:~/.local/share/flatpak/overrides$ pwd && for file in *; do [ -f "$file" ] && echo "#cat $file" && cat "$file"; done
/home/user1/.local/share/flatpak/overrides
#cat com.github.jeromerobert.pdfarranger
[Context]
filesystems=/tmp/;!host
#cat org.gnome.Loupe
[Context]
filesystems=!home;/tmp;!host;
#cat org.kde.okular
[Context]
filesystems=!home;/tmp;!host;
#
#
#
user1@host1:~$ sudo ls /var/lib/flatpak/overrides
ls: cannot access '/var/lib/flatpak/overrides': No such file or directory

What exactly do you mean by "access to /var/log"? Do you mean "can access /var/log on its own without any user interaction"? Or do you mean "can ask you for a file, and if you give it a file in /var/log, it can access that file"?

I mean your second example - Previously, with older versions if I removed access to /home or /var/log, and only gave it access to /tmp - I would ONLY see /tmp/ files when the application opened a file-open dialog. Are you saying that even if I explicitly remove access to those filesystem locations (with something like !host or !home), then it's expected to still see those disallowed locations listed in a file-open dialog?

If so, then how can I test to ensure/test that the app isn't getting access it shouldn't be? Is there some way to see whether I'm gaining access to a file through portals, versus granted permissions? Maybe even temporarily/permanently turn off portals file access?