What is the difference between a locked box and closing accounts in the working-capital adjustment?

the valuation date is fixed in the past (e.g. 31 Dec last year). The buyer takes on the EV from that date and benefits/suffers from the cash generation between the locked-box date and closing. Equity value = fixed at signing. The seller likes it (certainty). Closing accounts: working capital is measured at the closing date, and the buyer gets adjustments for deviations from 'normal NWC' (e.g. the average of the last 12 months). Equity value varies with the closing NWC. The buyer likes it (protection).

With a locked box, value 'as of the locked-box date'; with closing accounts, estimate the NWC adjustment in the bridge.