How about, no, it isn't. The astrology link you pointed to says:
> 1- they are completely idealized points moving in perfect circles around the sun without any physical acceleration except the Sun's, i.e.
> 2- they are subject only to the influence of the Sun and are not affected by the gravitational interactions of other large bodies.
This is not true of Ultima Thule, with a perihelion of 42.721 AU and aphelion of 46.442 AU. Its semi-major axis is nearly 10% larger than the mean solar distance of 40.998 you quoted.
The text goes on to insist that "things in Astrology work very well even though they do not or cannot physically exist", so why is there a need to have it exist?
Furthermore, user "Juan" points out the problems in the analysis, such as "it is obvious that the more asteroids you put into the equation, the more likely you will find one that resembles in its motion the orbit at least of Cupido". And the suggestion that 2000 KL4 matches Cupido.
How do we tell which is "really" Cupido?