Hi Adam1846,
First I see you have 3 listings so I took a Iook at them all as it seems you have no tubs in any of the 3.
I agree with @Shelley159 that I would leave the bath toggled off though oddly AirBnB has it showing a picture of a bath with a shower & not every tub has a shower. I think this is a glitch that no one in design ever thought of. My daughter-in-law prefers a tub too so I do understand your guest's disappointment.
Even shower gel is listed as an amenity, LOL
I would take the pictures of your shower and have the shower emphasized in pictures, like you have in 2 of your units. Pull back that shower curtain as it does appear in your first unit that it could be a bathtub. As well write a complete description under it emphasizing that you do not have tubs. I didn't see a picture of an outside shower as well.
I would consider more pictures to showcase what a nice place you have!
@Paula could push this along on her end as it seems to be something that guest would need to know shower. tub or both. If they can let people you have a Hot Water Kettle I would think that showers vs tubs would be appropriate request from hosts.
Hope this helps.