I think it’s just the standard to call free cash flow ebit*(1-t)+dep-FCinv-WCinv.
However, as mentioned previously this isn’t exactly true in all cases. A good valuation textbook should break this out, and IRCC, I believe schweser leaves a note when covering this to mention what I previously said. All non-cash expenses should be added back, but depreciation is just most common so it’s used in the formula. Also the main reason is that since this variation of our FCFF formula starts w/ EBIT, depreciation is likely to only be the non-cash charge that affects EBIT (not always true, however), while on the other hand if we start w/ NI, it’s more likely that there will be other non-cash charges that fall below EBIT, but are accounted for in Net Income (gains/losses are just one example.