Why is it unacceptable and wrong to take inflation into account together with discounting when planning financial and economic activities

If discounting of cash flow is taken into account when planning financial and economic activities, then impose inflation expectations in the forecast by multiplying current prices in business plan It would be wrong to look at inflation indices for planned periods.

Because the discount rate at which the same thing is carried out discounting for each time period (bringing the future value of money to the current one), already at least takes into account the inflation of future periods.

And if we evaluate the economy (business plan) by imposing inflation in our financial and economic model and simultaneously discounting money, then there will be a double bill, which is unacceptable and not correct, due to taking into account, in fact, the same factor, only in different aspects of calculating the resulting indicators.