Due to the nature of Qt libraries, which are not created by Apple, we can only offer limited support for Mari versions on macOS. As such, updating the macOS version of Mari required extra development time to ensure a quality user experience and we were unable to make a macOS build of 4.x in any version prior to Mari 4.6v2.
As Mari 4.8 and 5.0 move onto the 2020 VFX Reference Platform, we will no longer be able to support macOS beyond the Mari 4.7 line. For more information on this change, please see the following Knowledge Base Article