Just an observation here but I noticed after my last Ramp Test, intervals.icu (big fan!) calculated my FTP 4W higher than TR.
No biggie and after a couple of VO2 workouts, I think TR nailed my FTP but I am still a little curious about what’s driving the slight variation between the two platforms.
There is a dedicated thread to intervals.icu that is probably a better spot for your question
The difference is just a difference in estimation of FTP between the two programs (I know that’s what you want to know…the why) but isn’t large enough to be overly concerned about.