Bug in Completion_heads_engraver ?

[Graham King]

In the following code, I would expect the tie between the final two notes to be 
dotted.  The actual output is a solid tie.  Not sure whether this is a bug or 
just my doing something wrong...

\version "2.25.0"

{ c''2
  \once \tieDotted
  \set melismaBusyProperties = #'()
  1 ~ 2
}

\layout {
  \context {
    \Voice
    \remove "Note_heads_engraver"
    \consists "Completion_heads_engraver"
  }
}

I can work around this pretty easily, but I'd rather preserve the note 
durations of the original mensural notation if possible.

-- Graham