Hi @statistic_nerd,
(B- or P-) Splines are piecewise functions using polynomials, they do not require equal/regular timespaces as it interpolation will be done between those points : Spline (mathematics) So JMP can fit B- or P-Splines directly, without any data transformations.
The part you mentioned is about the calculation of specific metrics like Integrated Difference, RISE, RIFS, which require input values from 0 to 1 to calculate integral formula. If your data is not in the range 0-1, JMP will rescale/tranform your input data to have the correct range of input values with a formula like X' = (X - Xmin) / (Xmax - Xmin).
Hope this answer will solve your questions,
Victor GUILLER
"It is not unusual for a well-designed experiment to analyze itself" (Box, Hunter and Hunter)