I have nothing against ghosts, just against this type of ghost.
This is the user mailing list. For requests like "please fix this" you might
also send this to the bug mailing list. If you need a quick fix: Adding an
empty grace column \grace{ s } before the first note will fix this, as will
putting the whole thing into a single note chord <a'\laissezVibrer>. I suppose
that the Ambitus_engraver creates the Ambitus Note Heads in the same timestep
as the first Note Column, which results in them being acknowledged by the
engravers for semi-ties.
Cheers,
Valentin