Reverse breast envy? Sanae actually hers to be as small as Suwako?

Wonder if its reference to that Sakaki Chiyo-chan thing

Artist's comments @pixiv:
早苗 「諏訪子様のお胸も…その、小振りでいらっしゃるし…私のも育たないのかなぁ…。…揉めば育つかしら」

Sanae: "Suwako-sama's chest is so... well, it's so small... I don't think mine are growing, either... I wonder if they'll grow if I rub them?"