Trouble with xcoffins in TL2020

Consider the following MWE:

documentclass[11pt,a4paper]{article}
usepackage{xcoffins}
NewCoffinlcoffin
NewCoffinfcoffin
parindent=0pt
begin{document}
fbox{parbox{.25textwidth}{begin{enumerate}item This is a sentence which needs to be more than one-quarter the width of the text block and preferably wider than the whole width.end{enumerate}}}

SetVerticalCoffinlcoffin{.25textwidth}{begin{enumerate}item This is a sentence which needs to be more than one-quarter the width of the text block and preferably wider than the whole width.end{enumerate}}%
SetVerticalCoffinfcoffin{.48textwidth}{centering [a]par}%
JoinCoffinslcoffin[r,vc]fcoffin[l,vc](.02textwidth,0pt)%
TypesetCoffinlcoffin[T,l]par%

begin{enumerate}item This is a sentence which needs to be more than one-quarter the width of the text block and preferably wider than the whole width.end{enumerate}
end{document}    

With pdflatex from TL 2019, the result is as expected:

With pdflatex from TL 2020, the result is rather different:

The documentation for xcoffins indicates an update in October, but there’s no list of changes/revisions and I can’t see anything obviously different in the definition for vertical coffins.

Is this a bug or user error? If the latter, what’s the mistake?

SetVerticalCoffinlcoffin{.25textwidth}{linewidth=hsizebegin{enumerate}