Why IRRCalculation uses price with fees but without taxes for calculation?

[pfalcon]

Another of the series of "dumb questions" along with #4459 ? Why does IRRCalculation.java has code like:

    public void visit(CurrencyConverter converter, CalculationLineItem.TransactionItem item, PortfolioTransaction t)
    {
        dates.add(t.getDateTime().toLocalDate());
        long taxes = t.getUnitSum(Unit.Type.TAX, converter).getAmount();
        long amount = t.getMonetaryAmount(converter).getAmount();
        switch (t.getType())
        {
            case BUY:
            case DELIVERY_INBOUND:
            case TRANSFER_IN:
                values.add((-amount + taxes) / Values.Amount.divider());

?

There's logic in doing calculation with overheads like fees and taxes - it shows real IRR inside a portfolio. There's logic in doing calculation without any overhead - it shows securitie's own IRR. But what's the logic of excluding specifically taxes but not fees?

All that leads to situation like on screenshot, where IRR for trade shows one percentage, while Security Performance with the same single trade shows different percentage, while Absolute Performance finally shows value matching trade's IRR.