I was just curious as to why most serif typefaces that have a lowercase g with a loop are proportionally less in weight than the other letters. Is this to optically balance it out so it doesn't end up looking too big?
Yes (although more about weight than size). In a text face busy letters (like often the "s" as well) have to look lighter when large/magnified in order to end up looking the correct weight at small sizes.
Also, I believe a good binocular "g" must necessarily look a bit small and a bit vertically cramped in order to avoid more important things going out of whack across the font as a whole.
hhp
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