"Heavier flour" refers to a type of flour that is denser or thicker in texture compared to other types of flour. It may take up more space and feel heavier when measured in weight or used in baking. Full definition
I can't say because I haven't tried that blend, but that sounds like a mixture of heavier flours which might have weighed everything down! (simplyquinoa.com)
I feel that since we are not dealing with regular wheat flour, that the extra yeast may be needed for heavier flours such as the oat flour and rice flour. (yammiesglutenfreedom.com)
It sticks to the banneton even with heavy flouring with coarse flour. (theclevercarrot.com)