Is this actually still true? If you look at the public patch notes for ios and android, the number of platform bugs is similar.

I'm more thinking of architectural decisions rather than outright bugs, but yes it is improving - e.g. with projects like Treble.

How is comparing the security of Android, which is a far more open and diverse platform, to Apple, a walled garden, fair at all? And let's not forget about how Apple happily gives backdoor access to apps like Uber.

I'm not sure what "fairness" has to do with it.

Sure, Apple makes their own life easier in terms of security by applying draconian restrictions on the freedoms of their own users. But this and the fact that things are not as easy for Google to do effective security doesn't make it any less true that they aren't doing it.

Again, Apple's Uber backdoor isn't really relevant - I never implied Apple were benign, just that Google's security record is imperfect, and compares poorly.

The openness and diversity of Android's platform isn't a wholesale excuse for not securing users.

They're both smartphone platforms. Of course they're going to be compared to one another.