The IRR Matrix is still part of v0.81. However, Spencer opted to have the tab be automatically be hidden when the Development module is turned on. The reason he made this change is that he discourages using annual return metrics on opportunistic and value-add investments, and instead recommends monthly return metrics. This is due to the high volatility of the cash flows in the earlier years, which is not properly accounted for in annualized returns. Since the IRR Matrix only shows annual returns, he chose to have that tab hide when the Development module is turned on.
With that said, if you’d like to access the IRR Matrix, you can find it as a hidden tab. Simply hover your mouse over any of the tabs along the bottom of the Excel window, right-click and select ‘Unhide’, and then find the IRR Matrix tab in the list.