having a type is not the same thing, the essence of fetishizing is objectifying a body type without the consent or consideration of the person who owns the body

e.g. "it would be a shame to waste those great tits of yours" is a fetishization because it's only taking into account the viewer's perspective, not the owner's. a lot of trans men feel really dysphoric about having breasts and, quite frankly, it is only their business if they get top surgery or not. if they ask for your opinion, you can give it, but it should probably emphasize their happiness anyways because they're the ones who have to live in their body, at the end of the day

basically, as long as you treat the person you're seeing with respect and consideration for their happiness, you don't really need to worry about it