Ah, thanks!
interesting:
dt[1::6,{name}]; // {{"KATIE"}, {"LOUISE"}, {"JANE"}, {"JACLYN"}, {"LILLIE"}, {"TIM"}}
dt[1::6,"name"]; // {"KATIE", "LOUISE", "JANE", "JACLYN", "LILLIE", "TIM"}
dt[1::6,{height}]; // [59, 61, 55, 66, 52, 60]
dt[1::6,"height"]; // [59, 61, 55, 66, 52, 60] (same)
and therefore one needs to write:
dt[1::6,{name}] = {{"KATIE"}, {"LOUISE"}, {"JANE"}, {"JACLYN"}, {"LILLIE"}, {"TIM"}}
dt[1::6,"name"] = {"KATIE", "LOUISE", "JANE", "JACLYN", "LILLIE", "TIM"}
dt[1::6,"height"]=[1,2,3,4,5,6]
dt[1::6,{height}]=[1,2,3,4,5,6]
... I didn't know.