I was just reading through the statement of changes again, and what it actually says is:
- The changes to Appendix FM-SE don't come into effect until 31st December
- The change to allow electronic bank statements does NOT apply to Appendix FM-SE
- The change from 28 days to 31 days for the financial documents does NOT apply to Appendix FM-SE
Therefore, it looks there is no change at all to the financial requirement documents for a spousal/FLR(M)/SET(M) application.