Morris certainly came up with the gunwale detail before Kennebec did, as Morris was in business nearly 20 years before Kennebec. But as far as I know (which isn't as far as others perhaps), all Morris did was provide hulls from time to time, and didn't do any of the finishing.
To say somebody came up with a new feature just because they were in business first is silly. Morris may have been earlier to use this detail, but not because of this reason. However, Kennebec shows this feature in their first catalog of 1910. The earliest we can say for sure Morris did is 1911. And Carleton may have beat both to the punch...
We know Morris provided hulls for Kennebec in 1910
No, we don't know this. It has been speculated. It is one possible answer to the mystery of Kennebec canoes with splayed stems, but equally likely, barring further evidence, is that they were built in-house using Morris-like details.