The change is a breaking change.

Agreed to no fix in Dallas meeting.

There are other breaking changes in this version e.g. 0007892 changes the casing of Picoseconds which breaks the datavalue encoding.
With the argumentation of the "rare use", we can change also make the array encoding consitent between reversible Variant and reversible Matrix in Structures since it is a very rare case to have matrix in structures.

In Binary encoding and XML encoding are identical between Variant and Matrix embedded in Structures. Only the dimension information is at a different position in binary. The value encoding is the same.

For JSON reversable, we need to implement two completely different decoders for both cases which makes no sense for the reversable encoding. Especially since the Matrix encoding in Structures is very inefficient for encoding and decoding.

Made the variant encoding consistent by adding:
The ArrayDimensions field shall only be present if the number of dimensions is 2 or greater and all dimensions have a length greater than 0

Agreed to changes in F2F.

Since we work on a V2 JSON encoding, we make the encoding of matrix consistent between structure fields and Variant.

The new Compact and Verbose encoding using the same encoding for embedded Matrix and Matrix in Variant.

Agreed this is fixed in virtual F2F.