Possibly unwanted "stretchy" behavior in MathML output

[Lorenzo Bertini]

Hi,

my xhtml output trough the LyXHTML option had brackets that always
matched the height of the equation for paired \left( \right) brackets,
as one would expect, but also for plain ( ) ones, which is unexpected.
This of course led to the final output having some ridiculously sized
brackets. The problem is the MathML attribute "stretchy=true" added to
the output in both cases. I can't think of any reason why this would
be the intended behavior, especially since using \big( \big) yields
the requested bracket size.

I git-cloned the source (2.3.4), removed all the "stretchy=true" from
output-xhtml.cpp and built, and in the output there weren't any
height-matching brackets, but I don't know c++ too well and don't have
experience with this project code to make this happen only for \left(
\right) pairs. Can someone help me out?

I think it's system/machine independent but I tried it on Debian 10
Stable and Lyx 2.3.2 (Deb packaged); cloned 2.3.4.