Well, it probably has verified boot then. I see no. reason for a bootloader lock to exist without that.
Verified boot is a technology like Secure boot/Android Verified Boot, which prevents the device from running binaries with unknown signatures (they can also be specified in Secure boot and on certain android devices (see: Graphene OS, VBRoot)). While it only works for the kernel on Linux and Windows, the Android VB is way more secure, since it also verifies some system applications (also see Graphene OS).
The tech is better than just locked BL, because it also protects the device from kernel level malware, not just evil maid.
It's really interesting.
Edit: Also, thanks for the info. I'll wait until the price settles on the used market before buying one (but I doubt it will since it's a low volume device).