Well, to me it doesn't look good.
It needs a couple of readings but OK this is what I found so far:-
Here are the Immigration Directorate Instructions
And here's a link to the
Immigration Rules (paragraphs 297-300)
They do actually say the same.
To me, on a simple basis, it's a decision between Part 1 and Part 2 (don't want to get into the 'Compelling case' just yet)
The circumstances described (one parent settled and one parent limited leave) appear to more closely match Part 2 means Financial Requirement.
Can others please review and provide comment on their understanding?
Sometimes the more you read it the more confusing it gets
I still believe FM applies and still suggest you discuss further with that case worker.