On a personal note:
It makes sense really. Your fingerprint is like a unique password that you cannot change so HTC is doing everything prudent to protect that password for you. I don't see a problem with this personally.
On a technical note:
I believe the TZ partition (mmcblk0p11) has a check for whether the device is LOCKED, UNLOCKED, or RELOCKED. If it is anything other than LOCKED then the fingerprint scanner is automatically disabled.
I believe there are two possible ways to re-enable the fingerprint scanner:
- Issue the command fastboot oem lock from the bootloader then run a factory RUU for your carrier
- Hex edit the TZ partition to remove the unlock check, then fastboot oem lock and subsequently unlock the device again
The second method would require S-OFF to function as it is very unlikely that mmcblk0p11 is writable with S-ON.
I am by no means an expert with HBOOT or TZ so I may be way off base here, but that's how I see it right now. I'll see if I can get a warning posted in the threads about the fact that unlocking the bootloader with HTC Dev method will disable the fingerprint scanner.