Feature request: Cell Metadata

In the ECMA spec ( https://www.ecma-international.org/publications-and-standards/standards/ecma-376/ ), we have this:

When writing some formulas using openpyxl 3.1 with ArrayFormula, it ends up as CSE formulas, which is sometimes what I want:

However, sometimes I just want this, while still using ArrayFormula (to prevent unwanted @ from being added):

The difference in the XML is as follows:

The attribute cm=1 probably refers to this bit in metadata.xml

In summary, I would like to somehow write this metadata using openpyxl, so that I can have array formulas without CSE.