.. IAS ... does not represent the aircraft's true kinetic energy ..
Not so .. Hp, OAT, and wind are in the analyses. While the pilot might be predicating his activities on IAS, the complete sums are done in the background ... which gives you groundspeed etc and real numbers based on the data for the day.
The main concerns are
(a) variation in pilot techniques from those specified in the POH/AFM
(b) runway friction/slope characteristics
(c) accuracy of obstacle data.
FT data is based on smooth conditions ... ASI fluctuations is a problem for the guy in the field (but, in general, is not a significant concern)