Need help understanding rise time parameter in nc7wz04p6x datasheet
The 3ns rise and fall time is a specified test condition in Figure 6 used as a reference point for measuring the propagation delays for tPHL and tPLH. You will only realize the specified propagation delays if your input rise and fall time are 3ns or less. A longer input rise or fall time will result in different propagation delays (usually longer times).

The 25ns time that you found in the recommended operations conditions table is from the 5V at 5ns/V specification. This is the recommended slowest input rise time that the manufacturer specifies for the part so that you can realize good performance over normal operating conditions. Note that at this slowest recommended rise/fall time you will not obtain the nominal 2.3ns propagation delay.