I think the watch only works if you have an iPhone on you, which makes it redundant and pointless
I can think of many reasons to have one. . . especially for women who carry their iPhones in their purses. Phone call or text comes in. . . and they are forever digging in their purses trying to get their iPhone out to answer or check the text. Most often the call goes to message before they can get it out or they may drop the phone in fumbling for it. With the Apple Watch they don't need to constantly dig for their iPhone. . . They can see the text at a glance or answer the call.
Similarly, guys who keep their iPhones in pockets can merely glance to see if the text is important or answer without digging their phone out of their pocket all the time. There are lots of other functions separate from the iPhone. . . that tie from the iPhone or back to it.
Thefts of iPhones should drop with the use of the Apple Watch. . . the run by and snatch thefts won't happen with the watch being used instead. ApplePay will be easier and more convenient.
And, of course, you can use it as a time telling device with as many complications as you desire.
I am fairly certain you are correct. I discussed that very point with someone in the cellphone industry a few months ago, and he said the same thing as you regarding the need for a phone. The watch and phone connect via bluetooth.