Descriptions are sometimes unclear, and bathroom can mean various things, but if they specifically mention ensuite toilet but shared bath, then yes, it almost certainly means communal bathing facilities. However, not just anyone can see you bathe. It will only be members of your own sex.

In Japanese accommodations, particularly in traditional Ryokans, Minshukus, or older business hotels, a "shared bathroom" means that your guest room does not have its own private toilet or bathing facilities. Instead, these amenities are located in communal areas "along the corridor." Shared facilities are often separated by gender and include high-tech Japanese toilets and washbasins with mirrors. For bathing, this usually refers to a Sento (communal bath) or an Onsen (hot spring bath) where guests bathe together in a large tub after scrubbing down at individual stations. In some smaller guesthouses, the bath may be a single-use room that you lock and use privately in turn. It is essential to follow local etiquette: always wash your body thoroughly at the shower stations before entering the communal soaking water, and never bring your towel into the tub itself.