No, not at all. Both are different dishes with different masala powder.  People use the terms bisi bele bath and sambar rice or sambar sadam, probably because most of the spices used in both these spice blends are similar with varying proportions.  Bisibelebath powder has a few ingredients that are not used in sambar powder, such as marathi moggu (kapok buds), poppy seeds and sesame seeds that give a distinct taste and unique flavour to bisibele bath.  A wide variety of vegetables used to prepare sambar, whereas for bisi bele bath typically a handful of vegetables such as carrot, green beans, potatoes and green peas are used. Some prefer to add green bell pepper.