There is quite a lot of misunderstanding about what auditors mean when they sign off accounts as “true and fair”. For instance, they are not 100% certifying every number in the balance sheet and profit and loss account.
“True” means the numbers given by the directors are reasonably accurate to within a level of tolerable error. If the accounts of, say, BP had to be certified as accurate to the nearest penny, the audit fee would be prohibitively high.
“Fair” refers to the fact that a lot of judgement goes into a set of accounts. For example, working out the useful lives of assets for the purposes of calculating a “depreciation” charge involves a lot of estimation.
So auditors merely express an opinion that the accounts are fairly accurate and free from too much management bias.