Your logic is (almost) spot on. You have in fact highlighted the single point which I raised last November and blew a hole through literally decades of incompetent budgeting by ½ wits.
If the predicted (in Nov current FY) unallocated cash at bank at end FY is negligible (which it really should be in a well monitored, managed and adjusted budget) then it is likely to be a negligible consideration.
However! When the predicted (in Nov current FY) cash at bank 31 Mar is TWICE the clerk proposed precept for next FY, it “should” be obvious to all that ANY precept is wholly unjustified.
You wouldn’t imagine that would be a “hard sell” but it was like white man’s magic explaining this to the PC and even the IA was unable to grip the simple principle.
The problem arises when clerk and Cllrs have no credible financial management or budgeting experience.
Almost forgot - the only part you didn’t mention was taking some from the cash at bank cf balance to top up accruing EMRs