Hashimotos vs Graves

I've been a little baffled as to why there are two different names for this. The root cause seems to be the same- an autoimmune attack on the thyroid. This can lead to hypothyroidism or hyperthyroidism. So why different names?

If your autoimmune attack lead to hyperthyroidism, it's Graves. Otherwise, it's Hashimotos. But since the attack can lead to fluctuations between hyperthyroidism and hypothyroidism over periods of name why not just say "x" leading to hyperthyroidism, or "x" leading to hypothyroidism? It doesn't seem to me that two different names are needed.

I can't help but think that there is little more do it. So far the only difference I can really find is that anti-thyroidperoxidase antibodies are more common in Hashimotos and that Thyroid Stimulating Imunnoglobulin antibodies are more common with Graves.... but both can be present with the other.