It seems that only very specific variable names such as '10 metre U wind component' combined with '10 metre V wind component' are recognized as vector quantities. The naming standards for vectors are to my knowledge not documented and/or very limited. I recommend this is extended e.g. by combining similarly named variabled that have the words 'eastward' 'northward', 'x-component' and 'y-component' or U and V in their short or long names.
It seems that only very specific variable names such as '10 metre U wind component' combined with '10 metre V wind component' are recognized as vector quantities. The naming standards for vectors are to my knowledge not documented and/or very limited. I recommend this is extended e.g. by combining similarly named variabled that have the words 'eastward' 'northward', 'x-component' and 'y-component' or U and V in their short or long names.