Not all manufacturers are the same. In general, Google, Samsung or Sony sometimes lack, and ZTE or TCL is much worse when it lacks up to 4 (or more) patches compared to what they say.
As for Google, they told Wired that 'We have conducted a review of each OEM, see the device's compatibility certificate', and said it will investigate further. Google also explained some of the problems that SRL found out about ignoring the patch, that they might delete from the device, or some phones that lacked the official Android security certificate from Google.
Google sent to The Verge:
'We want to thank Karsten Nohl and Jakob Kell for their efforts to increase the security of their Android ecosystem. We are working with them to improve the mechanism of detecting situations where users choose other security updates instead of the one Google suggests. Security patch is one of many layers used to protect Android users. Platform-based integration methods such as application sandbox, security services like Google Play Protect, are equally important. These layers of security - along with the variety of Android ecosystems - also contribute to the researchers 'assumption that exploiting Android devices is still a challenge.'
See more:
Interested users download SnoopSnitch here.