I see, the letter is based on the Kentucky Resolutions of 1798, not the Kentucky Resolution of 1799 which I was referring to. Even still in that set of 9 resolution is an implicit indication of desire to preserve the Union and a stated dedication to that compact.
This still it centered on an enumerated verses implied interpretation of the Constitution which was a major issue of the time, and not secession.
You may be aware of the letter that the Continental Congress sent to King George pledging their desire to preserve their union with England and to settle their differences peaceably. The summer of 1775, after Lexington and Concord. King George didn't buy it and declared the Colonials to be rebels and traitors.
I'd put the wording of the Resolves in the same vein. An attempt to smooth over some very real differences when conflict was already baked into the cake. George Washington didn't buy the Resolves desire to preserve the union and could see that the Compact Theory of Jefferson and Madison implied nullification and probably disunion.