I just stepped into this, when trying to recover from nuked defaultuser environment ([Multi-user][Android] User data get deleted and lost, device reset).
I have a Xperia 10 II, with 4.4.0.68 (originally flashed with 4.4.0.64) and neither of the .68 nor .64 recovery images worked. The device is just stuck in a boot loop after flashing the recovery image to a and b sectors and rebooting.
I would like to access recovery mode before reflashing, to see if there’s data worth salvaging.