Why does the bootloader unlock error occur?

Question

Loaders

I have a Lenovo Tab 3 8 Plus (TB-8703X) tablet. I want to install TWRP3.2.1.

In the settings, the flag to allow unlocking the OS bootloader is enabled,

fastboot oem device-info gives:

(bootloader) Device tampered: false
(bootloader) Device unlocked: false
(bootloader) Device critical unlocked: false
(bootloader) Charger screen enabled: true
(bootloader) Display panel:
(bootloader) Device Verity Mode: enforcing

fastboot flashing unlock gives:

FAILED (remote: 'Need wipe userdata. Do 'fastboot oem unlock-go'')
fastboot: error: Command failed

fastboot oem unlock gives:

OKAY [ 0.016s]
Finished. Total time: 0.016s

erases as expected and immediately installs the software installed at the factory.

Finished check via fastboot oem device-info gives:

(bootloader) Device tampered: false
(bootloader) Device unlocked: false
(bootloader) Device critical unlocked: false
(bootloader) Charger screen enabled: true
(bootloader) Display panel:
(bootloader) Device Verity Mode: enforcing
Question: how to unlock the bootloader? Where is the mistake?
Sincerely,
Radmir.

Answer 1

The addition of
the fastboot flashing unlock command gives an error and after that the command:
fastboot oem unlock-go cleans the memory, ... and immediately installs the software installed at the factory.
The bootloader is not unlocked - you can not install TWRP!
Instead of the fastboot flashing unlock command, you can do fastboot flashing unlock_critical , it passes without error and the factory software is automatically restored again. Still no unlock.
You can not install TWRP!
Variations
1. Is it possible to install the TWRP bootsigned version through the QFIL program? Doesn't it hurt to not unlock?
2.Or maybe put TWRP.zip using CWM menu item Apply Update from sdcard? I heard that the latest TWRPs do not spoil the boot, system partitions? And will the lack of unlocking interfere?
Sincerely,
Radmir.