The dropped tenor banjo tuning may have been one of his inventions for the Irish banjo.
Elmer Snowden adopted that tuning for jazz playing when he was the founder of the Washingtonians.

I prefer the sound of the dropped tenor GDAE in preference to the screaming high
tenor CGDA.

Gerry O'Connor uses the standard tenor banjo CGDA but I always thought that
the dropped tenor tuning filled in better with a mellow sound. It's a matter of preference.

McKenna was an innovator.