It's described more in the report. Their assessment #6 hinges on - "Very likely" poor or non-existent robust GPU support, - Unlikely robust support for specia

It's described more in the report. Their assessment #6 hinges on - "Very likely" poor or non-existent robust GPU support, - Unlikely robust support for specialized processors (i.e., non-general purpose CPU) like "Data Flow processors" and "processing in/near memory", - Fortran advocacy and advancement is likely limited to DOE, which the report implies is insufficient, and - Vendors of hardware have prioritized C++.