Microsoft has three versions of the OOXML specification and this meta bug is for issues related to the first version they created that came with Office 2007. LibreOffice follows the OOXML transitional specification which came with Office 2010 and there is separate meta bug for the OOXML strict specification (bug 83571).
Michael Stahl committed a patch related to this issue.
It has been pushed to "master":
tdf#107841 oox: rename ambiguous and confusing ECMA_DIALECT
It will be available in 7.6.0.
The patch should be included in the daily builds available at
https://dev-builds.libreoffice.org/daily/ in the next 24-48 hours. More
information about daily builds can be found at:
Affected users are encouraged to test the fix and report feedback.