Are either of those using EFI with secure boot? According to the bug
report, that's the trigger.
I believe you are right. To my surprise, after inspection of the BIOS
displays in the machine that does allow data access, I find no mention at
all of secure boot capability.
The machine that does not allow access to /sys/kernel/debug/usb/devices
supports secure boot, although I think it used to provide access to this
data. Some configuration change to the secure boot facility is the
likely explanation for this variation.