The data will only be indicative of 'reliability' if you limit yourself the those data sets you wish to define as related to 'reliability' and disregard the rest.
Also, do not be misled into thinking the 6000-odd vehicle failures were comprised of the same number of individual defects. The detailed figures include "advisories" and many vehicles would have failed on multiple defects.
E.g. the 22,925 Transits presented for test (of which 6,987 failed) accumulated 16,614 defects of which 207 were Body & Structure, 2,113 Brakes and 2,512 View of Road etc.