This has been fixed and is available for download here
Starting from MG-PickerStudio.MacOS.releaseDate20220516.zip, the plug-in bundle files have been notarized by Apple.
But due to the nature of the Maya plugin .bundle extension as it is used as an executable Mach-O file, the notary ticket cannot be stapled, so when you install the tool, make sure your machine is connected to the internet so that the macOS gatekeeper will go online to check the notary and cache it. This is a one-off process, and all you need to do is if the gatekeeper warns if you want to load the downloaded .bundle file, press the "Yes" button.