First, I believe the recommended values you are citing in the range of 60-80mm/s to be based on 3D printing and other typical maximum work speeds. That is limited by the process parameters and of no relation to the linear modules.
Here is a citation from Snapmaker staff, of which I’m aware you were in this conversations but I want to link it here for reference:
A recommendation to not exceed sustained 100mm/s, but acknowledging 120mm/s is achievable: Speed Limits on SM2? - #11 by whimsycwd
Just quickly redoing the math to skip straight to the conclusions you get the following (v1 max of 100mm/s, v2 scaled appropriately to 250mm/s)
v1 min segment distance for full speed: 10mm
v2 min segment distance for full speed: 62.5mm
v1 time to travel 62.5mm: 0.73s
v2 time to travel 62.5mm: 0.5s
A quite small difference in time of only 0.23s (about a 32% speed up) for something that would be only a high speed travel and never an extrusion move.
Even with a wild assumption like “printing at only 60mm/s wasn’t achievable before, but now it is somehow possible to print at 90mm/s” the speed up is only for very long segments capable of reaching the max speed. And running with that assumption that the print job is capable of reaching that max speed on every move puts the maximum possible speed up around 40%.
That 40% is unrealistically high, but any further meaningful estimation would require considering typical model geometry, as this is for an ideal model designed specifically for printing as fast as possible, and also is making fundamental assumptions that are provably false regarding how the fused filament process works.