Agreed to a degree, but from a personal point of view, I think that Davies would have been even more uncomfortable if he had had to give Johnston seniority. The chemistry between the two of them just was not right, they had quarrelled from the earliest day of their aquaintance, when at West Point they both had courted the daughter of the tavern owner Benny Havens. Then later, as Senator, Davis would have preferred another Johnston, A.S. Johnston, to get the position of Quartermaster General in the US Army. Instead of Albert Sidney Johnston, Joseph Eggleston Johnston was appointed that position. Not to deviate too much from the original intention of this thread, but there is a pretty good article shedding some light on the conflict between Johnston and Davis:
https://archives.columbusstate.edu/gah/1993/72-81.pdf
I guess that Davis was pretty contented that he could find a reason why he could put Johnston a step farther down the ladder.