He has a spreadsheet to keep track of finances (I don’t have access to it, just see him updating it).
So… he’s saving for something (joint finances related, like a holiday or house upgrade, or for himself?), he has a spreadsheet he updates so is aware of and tracking finances - he’s not lazy and just hasn’t bothered to make it equal, it seems like to me. It doesn’t sound like it’s a lack of financial literacy.
But that’s an outsider’s perspective.
You say you’ve always been happy with it - are you happy with not knowing exactly how the financial future is set up?
At a minimum the savings should be 50-50 or in joint names, you should have visibility over the family financial state of affairs (even if you’re not the one doing the detail or day to day stuff) and you should be investing in a private pension or other form of investment for you, not just him.
I’d put my foot down firmly on this - get him to show you the spreadsheet, go through twist is held where, insist on setting up savings accessibly for you as well as him - and if nothing changed you’d need to wonder if it was, in fact, not quite so harmless as you’d presumed. Because none of that is difficult to do and there’s no reason not to.
If he can update a spreadsheet he can leave a greater float in the joint account and put the savings into joint names.