My guess is that the Chromium release engineering "team" (it might just be one person) is a volunteer who gets paid to do other things.
In my case, I use the Marmaduke ungoogled-nosync Chromium build from Woolyss (both Windows 10 64-bit and macOS 64-bit). Sometimes his builds show up a day or two later, sometimes a week goes by. At least once there was no build for two weeks after the Chrome release; I assume he was on vacation. Sometimes the macOS build shows up first, other times it's the Windows build.
A more stark example: the GIMP image editor. The GIMP engineering team continues to release new versions and the Windows release team seems to have an installer ready to download upon release. However the Mac distribution is stuck on version 2.10.14 which is nearly a year old. It appears that the GIMP project lost their Mac release engineer.
The code is there so if you're a Mac programmer you can build it yourself (I'm not adept at such endeavors). But there is no one who has stepped up to the plate to make a publicly distributable macOS package of the current GIMP.
Feel free to ask the Chromium development team directly. I'm guessing you will get a response like "we are always looking for volunteers to help with our development efforts."