With the update from systemd 204 to 207 the boot.mount unit generated by the efi-boot-generator is always started, so the automount has no effect. "systemctl show /boot" shows that WantedBy is set to the ESP device, meaning the mount is pulled in by the device itself. It seems like overriding Options=noauto with a drop-in snippet fixes this. btw, is the default Options=umask=0077 set on purpose? This is kind of annoying because you can't get into /boot without root privileges and it doesn't match with the default permissions on /boot (at least on Arch Linux).
Thanks for the report. This should be fixed by: http://cgit.freedesktop.org/systemd/systemd/commit/?id=0b9e3f2cfdd8bc365f98e5544c7c3f5ac94d0965
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