Nah AGT and Picard don’t happen in the same timeline. AGT was some sort of alternate timeline. But the events of the Prime timeline diverge enough from the AGT timeline that it makes more sense that the new warp scale was unique to the AGT timeline and didn’t happen in the Prime.
The TNG Technical Manual explains the change, it went from a cubic function to a logarithmic function along with some technobabble justification for why. There’s also some interesting background info and formulas on Memory Alpha, apparently the scale change happened in 2312 according to some magazine.
The scale changed from TOS to TNG. Then in All Good Things which is the only other time we’ve seen it presumably they changed the scale again.
To be fair, it does make sense.
“Warp 9.975” (and beyond, for newer ships than the Intrepid) is getting a bit absurd
And then back for Picard when the max sustainable is warp 9.99.
Nah AGT and Picard don’t happen in the same timeline. AGT was some sort of alternate timeline. But the events of the Prime timeline diverge enough from the AGT timeline that it makes more sense that the new warp scale was unique to the AGT timeline and didn’t happen in the Prime.
They certainly exist separate of each other. That we all have to call into question the timelines is half the fun.
Concerning times they exceeded warp 10 in TOS:
The narrative awareness and scaling has changed over time. I imagine largely due to people like us.
The TNG Technical Manual explains the change, it went from a cubic function to a logarithmic function along with some technobabble justification for why. There’s also some interesting background info and formulas on Memory Alpha, apparently the scale change happened in 2312 according to some magazine.