The whole post is so dumb (especially this one) I cringed while reading it.

He’s talking about a feature, admits its good, and then says most people won’t use it much. How is other people using a feature a considering when buying a product?

Security? No. Privacy? Of course (assuming you don’t use vanilla FF). Is it much easier to escape the sandbox in Gecko than Chromium. Doesn’t matter what options they give you in the settings titled “Security”.

They don’t care.

Most apps choose to distribute through Play Store only though. If the devs aren’t officially distributing on a separate platform or provide signing keys for you to verify the signature of the APK you get from elsewhere, you’re just asking for malware by downloading it anywhere else.