= your budget is adjusted = then the per turn costs are spent
This can, and in a recent game did, lead to an immediate negative funds on hand without having a chance to adjust things. For example having big ships under production. This can also give negative prestige affects for the negative balance.
The request is to delay the post-war budget adjustment to after the ending month. This would avoid the instant negatives. The budget would still be adjusted just after the end-war-month.
Think of it being that on day 01 the war is on with the monthly budgets set. A treaty is signed say on day 15. The monthly budget agreed runs for the remaining 2 weeks and on day 31 the Ministry of Finance says they are doing the drop of military budgets at this time. So day 01 of the month end-war+1 is now going to need a lot of work from the Admiral to make a balanced budget.