You may be right, but absent any documentation of what Davis et al were thinking I would be inclined to disagree. Considering that the majority of newspapers (northern and southern) were promoting the idea of a peaceful separation, I can only speculate as to the reason for the buildup. For now, I would think that Davis overestimated the speed of a military response.
This is pretty well supported in the record. Davis wanted the border states to join the rebellion. He wanted a shooting incident to incite them, and that is pretty much what happened. Davis and the other traitors wanted to act while the secession fever was still red hot. That is why they fired on Fort Sumter when they knew full well that they could starve out the fort within the -week-.
Too, Davis had Kentucky invaded when that state wanted to remain neutral-- making a clear mockery of any pretence of 'states rights'.
Walt