Meaning of 'OpenBSD -stable binary packages'

Hello all.

I am running 6.5 STABLE.
This release was with PHP 7.1.28. So my webserver runs PHP 7.1.28.

Today I wanted to install an additional PHP driver for postgresql and I
realized that there are only plugins for PHP versions 7.1.31 and 7.1.32
(and 7.2.x + 7.3.x) available with pkg_add.

So my question is if the new announced binary updates for packages means
that the released versions are gone?
Do I have to edit /etc/installurl to follow -stable without the updates
for packages?
Have I misunderstood the mail on the list about the binary updates...