to be honest: not 100% sure 
it’s mentioned several times - e.g. here (wiki) and here (under point 3 Unlock your bootloader)
But you’re right - there was a change with an update. But nevertheless - I thought the second command-based unlocking-part (fastboot oem unlock) - which ereases all your data - is still necessary…?
(I’ll install LOS on my FP3 within the next weeks so I didn’t had to unlock my bootloader until now 