You're correct there is no tub symbol and none of the standard Balcony cabins that have tubs seem to display a tub symbol, but yes they are scattered around on the Seashore as well.
I know this particular cabin does have the tub because I've seen a video walkthrough of the cabin and it has the larger bathroom footprint and has the smaller loveseat and not the larger sofa.
I've always assumed, maybe incorrectly, when booking a guarantee cabin that if you had more than the standard two passengers that there would be a bed for the 3rd/4th passenger. Indeed it may be a sofa bed, pullman bed, etc. I'm unaware of any rollaway beds on the Seashore.