Plant an error in December’s books and see whether the trial balance catches it.
$42,300 vs $42,300
No
The trial balance still balances at $42,300. Equal totals do not mean the books are right.
A lists every account and its balance, debits in one column and credits in the other. If posting was done correctly, the two columns total the same amount: $45,300 for FastForward at December 31.
Equal totals only prove that debits and credits match in the aggregate. A transaction that was never recorded, one recorded twice, or the right amount in the wrong account on the same side — none of these unbalance a trial balance. Only an error that hits one side and not the other shows up as a difference.