Unrelated. I don't know what all mtier provided, but chromium port updates are not backported to -stable. A quick check indicates they did not provide this.
Also note that mtier announced they will no longer be providing -stable packages of their own.
If you want the latest chromium, you need to run -current snapshots. Packages are available. Chrome is enormous dwarfing the OpenBSD kernel and base system combined and is under constant development, it's a challenge to keep updated on -current, let alone attempting newer versions on -stable.
Also note that mtier announced they will no longer be providing -stable packages of their own.
https://twitter.com/mtierltd/status/1161639634587279360
If you want the latest chromium, you need to run -current snapshots. Packages are available. Chrome is enormous dwarfing the OpenBSD kernel and base system combined and is under constant development, it's a challenge to keep updated on -current, let alone attempting newer versions on -stable.