Op-Amp Unity Gain Frequency
You are correct about rise time and slew rate being almost the same thing - sorta kinda maybe.  The slew rate spec probably does not have any limitations on it, so it can be used to calculate the transition time for edges of any amplitude.  The risetime spec probably has a qualifier on it, like risetime for a 5 V pulse, or risetime with +/-5 V power rails.

Also, risetime is the transition time for the entire 10%-90% part of the waveform.  But, the slope of the waveform is not constant throughout.  It slows a bit at the top and bottom as it begins its transition to the flat parts of the pulse.  Slew rate can be thought of as the slope of the waveform at its fastest part (usually a small part in the middle).