That might be true, I only read Wikipedia, but Wiktionary is probably right. That said, they might mean the same.
They are not the same in the norse religion, but maybe they were the same goddess in the western germanic religion. In this latter area was where the so called "Interpretatio germanica" happened (the germanic tribes adopted the roman calendar using their gods instead of the ones of the romans). Maybe after Scandinavia was christianised this confusion appeared.
I checked for Ancient Persian weekdays names and the English words r like translation to the Ancient persian astral calendars. The sun mon... are the list of planets and sun and moon together. But seems the other Indo European people have named their gods after planets or vise versa. And fri = frig = Venus in that system.