What is wrong with my .path setup?

[John Ioannidis <systemd-devel@xxxxxxx>]

Here are my .path and .service files:

$ cat /etc/systemd/system/trigg.path
[Path]
DirectoryNotEmpty=/root/trigger
MakeDirectory=true

$ cat /etc/systemd/system/trigg.service
[Unit]
Description=Trigger Service

[Service]
ExecStart=/usr/bin/touch /root/wastriggered
Type=oneshot

Now, after robooting, I would have expected that /root/trigger would exist; it does not. And, of course, creating it manually and touching a file in there does not trigger the path.

What am I missing? I have successfully used .path units in the past, and what I'm doing here looks right; unfortunately I do not have access to those old machines any more (previous employer).

This is all on a fully-patched Ubuntu 20.04LTS machine:
$ systemd --version
systemd 245 (245.4-4ubuntu3.15)
+PAM +AUDIT +SELINUX +IMA +APPARMOR +SMACK +SYSVINIT +UTMP +LIBCRYPTSETUP +GCRYPT +GNUTLS +ACL +XZ +LZ4 +SECCOMP +BLKID +ELFUTILS +KMOD +IDN2 -IDN +PCRE2 default-hierarchy=hybrid