The bank of England who are politically independent of the government consider it to be daft as do the opposition leadership. Many journalists on both sides of the political polarity also consider it to be daft. I think even the civil servant that leaked the budget early probably thinks it's a bad idea. (They want to find who it is and send the person to jail)
I'm not an expert myself, I would say lifting the spending cap for universal credit recipients with more than 2 children would be like giving them a third breadwinner. If you freeze my earnings allowance at twelve and half thousand and I get a pay rise in spring, that would mean I pay more. They set it up so everyone will pay more after spring 2026. I don't know much but I know that if you take money from one person and give it to another, you're not creating more money or jobs.
It's not too late to change it if they think it is wrong.
Good luck and godspeed to them all.