If I understand the question correctly -- why did I suggest
commodity= for a measurement of height but not for weight -- it's not
a novice question at all.
My thinking (which may be muddled by lack of sleep) is that for
weight, we don't normally express the commodity, which is really
"person". But because with weight or mass there really can only be
one measurement for a person (leaving aside all sorts of nuances like
being weighed in the morning vs evening, with vs without clothes,
etc.), I felt, perhaps incorrectly so, that it was OK to let that bit
of information be implied by the fact that the entire table of data
is about people.
In truth, when measuring height, the commodity is still "person". But
for the height, unlike weight, the unit does not tell you what
direction you're measuring. The unit measures distance, which could
be height, width, depth, or circumference. So I thought in this case
it was better to supply the information explicitly. Perhaps it should
be on type= instead.
Enough babble. Time for sleep. G'night.