Length of underbracket with Libertinus Math

The combination of Libertinus Math and underbracket (provided by mathtools) produces unreasonably large brackets if the argument of underbracket becomes too long.

(One can probably also argue that in the second to fourth example the bracket is a bit too short.)

The same output occurs with Uunderbracket (provided by unicode-math) instead of underbracket.
The problem also occurs with overbracket and Uoverbracket.

The problem does not occur with underbrace or overbrace (but one could again argue that some of the braces are too short).

It this a problem with Libertinus Math (which I would then report to the developer) or a problem with mathtools / unicode-math (in which case I don’t know what to do about it)?

---

documentclass[a5paper]{scrartcl}


usepackage{mathtools}
usepackage{unicode-math}
setmathfont{Libertinus Math}

begin{document}

noindenttexttt{underbracket}
[
    underbracket{a}
  + underbracket{ab}
  + underbracket{abc}
  + underbracket{abcd}
  + underbracket{abcde}
  + underbracket{abcdeh}
  + underbracket{abcdehi}
  + underbracket{abcdehik}
]
texttt{Uunderbracket}
[
    Uunderbracket{a}
  + Uunderbracket{ab}
  + Uunderbracket{abc}
  + Uunderbracket{abcd}
  + Uunderbracket{abcde}
  + Uunderbracket{abcdeh}
  + Uunderbracket{abcdehi}
  + Uunderbracket{abcdehik}
]
noindenttexttt{overbracket}
[
    overbracket{a}
  + overbracket{ab}
  + overbracket{abc}
  + overbracket{abcd}
  + overbracket{abcde}
  + overbracket{abcdeh}
  + overbracket{abcdehi}
  + overbracket{abcdehik}
]
texttt{Uoverbracket}
[
    Uoverbracket{a}
  + Uoverbracket{ab}
  + Uoverbracket{abc}
  + Uoverbracket{abcd}
  + Uoverbracket{abcde}
  + Uoverbracket{abcdeh}
  + Uoverbracket{abcdehi}
  + Uoverbracket{abcdehik}
]
texttt{underbrace}
[
    underbrace{a}
  + underbrace{ab}
  + underbrace{abc}
  + underbrace{abcd}
  + underbrace{abcde}
  + underbrace{abcdeh}
  + underbrace{abcdehi}
  + underbrace{abcdehik}
]
texttt{overbrace}
[
    overbrace{a}
  + overbrace{ab}
  + overbrace{abc}
  + overbrace{abcd}
  + overbrace{abcde}
  + overbrace{abcdeh}
  + overbrace{abcdehi}
  + overbrace{abcdehik}
]

end{document}