The wording you describe sounds like the standard email used for everyone at the stage when the CO is coming towards the end of processing. So it doesn't take any account of the fact that in your case, very little time has passed since the application was allocated. And there's nothing to worry about in the use of the word 'required' - it only means 'we must have', so it's no harsher than if they'd said 'upload this' or 'send that'.
The CO is in the position of having to tick the boxes on a list of what needs to be done/seen. Once the boxes are ticked, s/he can proceed to a recommendation. If she left out any, when the case went for second-person checking, the 2pc official would send it back for correction because she'd missed part of the procedure. Neither the CO nor the 2pc official has the power to make allowances for the fact that in your case, it's only been three weeks, whereas for some people, it would have been getting on for a year. So bear in mind that you're having to go through the motions for the sake of it, and these requirements aren't based on any extra particular doubt of your situation. If it were me, I'd help the CO with the paperwork as far as possible, and if this meant doubling up of what I'd already provided, then I'd do it, for instance by asking the people who'd already provided support letters to give another one. These can state that the pair of you are STILL living together over these recent weeks since your application went in. That shows willing. Yes, you can point out to the CO that x, y and z evidence you have already submitted fills the requirement, but if you CAN give them more, do it.