The link you share from Motorola webpage is also tried it is not working.
The steps proved in the motorola webpage works fine for Moto g5, g6, g7 which i have already rooted it
These g series are having Qualcomm chipset.
Moto e6 is having MediaTek chipset. Hence i asked your support.
Attached screenshot are the from motorola webpage which they tell booloader unlock is supported.