People can be attracted or turned on by various things...sometimes those things fit together, but they can even be pretty much mutually exclusive.
I don't think it so odd that some people prefer a more middling size range, but are still always turned on by gain at any size.
I do think it is odd that someone would tell anyone that they were too fat for the speaker's preference, but then keep encouraging them with their gain. To me, that is just rude. If you know them well perhaps admit that they've exceeded your size preference but that their gain still turns you on, so that they know where your head is at. But then don't keep encouraging them