Way to alter the asset base of ROI

Sir, I read the following explanation about ROI in the textbook. If a manager's large bonus depends on ROI being met, the manager may feel pressure to massage the measure. The asset base of the ratio can be altered by increasing/decreasing payables and receivables (by speeding up or delaying payments and receipts). My understanding is: The asset base of the ratio refers to 'Capital employed' which is always equal to either 'Total assets minus current liabilities' or 'Non-current assets plus working capital'. So the base can be altered by manipulating payables since the denominator of the formula changes depending on the amount of payables(=current liabilities), which leads to, for example, more current liabilities --> lower denominator --> higher ROI. But for receivables, I don't think that manipulating receivables will impact the asset base. Because 'Capital employed' includes cash, and cash is related to receivables. So whether you choose to delay collection of receivables or collect cash immediately, both should result in the same base as receivables will eventually be converted into cash. Could you tell me what is wrong with my understanding?