Pension provisions IFRS | Tax effect

Hi guys, By linking accounting and rating I came across an interesting fact. Rating agencies like S&P seem to account for a pension deficit (Plan assets < DBO), deducting a "tax effect" by simply multiplying the pension deficit with (1-effective tax rate) when looking at total debt. My understanding so far was that service costs (current and past) and net interest costs are charged to the P&L directly and thereby reduce the taxable income. In addition, re-measurements of DBO are charged to OCI – tax effect reported but booked in deferred tax assets / liabilities, correct? So it is unclear to me how one could explain the "tax effect" of a pension deficit that is recognized by S&P? This should be related to the timing of recognition of taxes in the cash flow statement. Would highly appreciate your help! Best, Jonathan