fastboot oem lock topic

So I decided to lock the bootloader since I will be traveling, but I thought locking will not wipe the device, is there a bug on NEXUS 6 because I locked it and as soon as I reboot the device it went into erasing the device and started in the welcome screen.

I tried to search the forums and google but all I can find was that the device will not erase anything when you do the fastboot oem lock.