My understanding for the change to 10,000ft (as seen previously in ARFORs) was for standardising the products globally.
e.g.
https://www.metoffice.gov.uk/aviatio...charts-details
If you're flying above 10,000ft the GAF isn't applicable so why include information that can't be used in conjunction with the rest of the forecast? If you're higher than 10,000ft you can use the grid point wind and temperature forecasts to find the freezing level.