Why is it possible to backup the rom images from mediatek devices using third party (open source) tools such as SP flash tool unlike Google Pixel? When running Linux i am able to use SP flash tool to do a readback from my mediatek device and do a full backup of the rom images while the device is in preloader mode, without the use of any additional USB drivers.
Yet this is not possible with Google Pixel.
Is this perhaps due to Mediatek going out of their way and adding support for their devices during the development of the mainline linux kernel and Google dont?
it is simply not true that linux does not need drivers. linux is just smarter than windows and handles it's drivers itself. linux just doesn't ask for drivers, but it use drivers anyway
new mediatek devices are accessable from preloader only with proper secure boot download agent (DA_SWSEC.bin) and authentification file (auth_sv5.auth). that files are vendor and device specific. even with proper files SP Flash Tool is not able to read back whole EMMC, there are forbidden partitions which can't be accessed. Lenovo devices are a good example
for qualcomm devices it is quite same, there we have EDL mode available instead where we can read raw partitions from device only with proper factory loader (firehose programmer). again that files are vendor and device specific
the fact that you can't read data from google pixel is that HTC hasn't released/leaked firehose programmer for google devices
while google may have that file internally, it seems they are not interested in unbricking, the official install method rely on fastboot only. once a device becomes bricked, it is not possible to unbrick (on locked bootloader). so the official solution for bricked google devices is a replacement device. that's why i personally recommend every google device should be bootloader unlocked on initial setup (my opinion)