mathtools aims to fix bugs and problems with the AMS package set.
Quote from the AMS site http://www.ams.org/publications/authors/tex/amslatex:
In 2016, LuaTeX version 1 was released, and attempts to use amsmath with LuaLaTeX would fail. To address this problem most effectively, responsibility for maintenance of amsmath was transferred to the LaTeX Project, and the authoritative version of amsmath is now on CTAN and in TeX Live.
Which fix has made it into the AMS package already?
Can the LaTeX Project merge the fixes to amsmath?