Looking at `mtkclient`'s README, it _is_ necessary to unlock the bootloader before flashing an unsigned image.
I can't tell how it's possible to get past the unverified boot warning. I've edited the tutorial, but it's still important to unlock the bootloader before rooting or flashing non-OEM boot images.
The only conclusion I've come to is that Andy's Astro has had some sort of prior modification we're/Andy's not aware of. Possibly factory. Did it come pre-installed in Chinese or have Deejay-dota installed?
I think you are correct.
The bootloader can't prevent images from being flashed, it just prevents unsigned images from loading. My answer to this question has some details on the way locked/unlocked bootloaders work.
MTK Client communicates with the bootloader of MediaTek devices to flash images, the lock status of the bootloader does not affect ability to flash. (It is still possible to block flashing by only allowing signed binaries to communicate with the bootloader) But , if an unsigned image is flashed, the bootloader will refuse to load the image. This case is really a big surprise. I don' t know how the multi boot of Cosmo works, but I think cosmo can boot unsigned images. ( PC probably made changes ). In astro slide who knows ?
Most of the times images are flashed using Fastboot (even when there are more options to flash like "SP Flash Tool and MTK Client ") And Fastboot checks most of the times if the bootloader is unlocked, and only lets flashing images if it is unlocked. Mine is unlocked with orange state. So I cannot verify if using only MTK client tool will boot astro without this warning or will refuse to load the unsigned boot image.
As I know Just to clarify I think MTK Client tool connects directly to your CPU Firmware prior to booting up the device.
Please see what happened to me :
I have unlocked my phone and did a root on it. After this some apps like bank apps and others were not working. I decided to do a reset on my phone and after this I did a lock to oem again. After this the phone was bricked booting only in fastboot mode. ( like a bricked phone ). So, I have unlocked the oem again and for my surprise android returned. So, do not lock oem after you unlock it.
And do not edit lk file to prevent the warning orange state. Please don't do this. After I did his, the smartphone did not turn on anymore. It didn't even go into fastboot mode. I thought : Now it's gone. Luckily the mtkclient that was installed on my linux recognized the smartphone and I restored the old file. This is why I think MTK Client tool connects directly to your CPU Firmware prior to booting up the device.