Because Newtonian mechanics states without equivocation orbits are ellipses. And if Universal Sandbox was indeed using Newtonian mechanics the orbits would ellipses or "helical," not a vortex or a helix.
But the orbits rendered in your submitted model are vortex.
The understanding here can be reached by understanding "local frame of reference".
Sun and orbiting planets don't revolve separately around galaxy core.
Look at Earth and Moon.
They are not orbiting Sun separately, but as a system.
Within the system Moon is still following its elliptic orbit relative to Earth.
Jupiter with all its moons also makes system that revolves around Sun as a whole.
During that movement every Jupiter's moon follows own elliptical orbit relative to Jupiter.
Same goes for all planets and other objects orbiting the Sun.
Solar system orbits galactic core as a whole.
Paths of planets of Solar system are helicoidal relative to galactic core, but elliptical relative to the Sun.
Just like each planet moons have spiral paths relative to the Sun but elliptical relative to own planets.
Example of Sun-Earth system:
Within Solar system reference frame Earth orbits Sun on elliptical path.
But relative to galactic reference frame they both additionally have velocity component of orbiting galactic core.
That component is equal for both, Sun and Earth, and doesn't influence their local interaction.
Our present knowledge about Universe couldn't be developed while religious Dogma was active.
If revolution around galaxy core takes 225 million years, and our heliocentric observations last 400 years,
then during the whole observation period Solar system traveled (360/225 million)*400 = 0.00064 degrees on own orbit.
It is 2.3 arcseconds for entire 400 years, or 0.00575 arcseconds per year (1.597E-6 degrees).
Error of 0.000001597 degrees is 1.6 ppm (parts per million) yearly, or 365 times smaller than that daily, which is 4.38 ppb (parts per billion).
Not enough to be measured during formulation of Kepler's laws.
Too close to straight line.
During our routine calculations within inner part of Solar system it sounds pretty tollerable to me.
I don't know if, for the probe New Horizons sent to Pluto, they took the correction into calculation.