...or rather, switch back, since the TNG-era warp scale was used on Enterprise...
Uh, no, it wasn't, not really. We never got any ENT references to "warp 10 is infinite speed", and we never got any specific references to which warp factor would match which speed.
Not entirely correct, We got the "Neptune and back in six minutes" quote from Archer who clearly used it to point out the speed of the Enterprise a ship designed with a top speed of warp 5. We can calculate the now speed because we know the distance to Neptune, it turns out that it takes a warp factor between 4.5 to 4.7 (if we take the proposed TOS scale) to make the trip in six minutes, depending on the relative position of the planets in the solar system.
We also have Archers quote of going 30,000,000 kilometers per second, which also translates to 4.5 on the TOS scale.
Although this may not be conclusive it at least shows that the writers used the proposed TOS scale to calculate their speeds in ENT and in doing so kinda validates the scale (at least for ENT and unless you want to argue that starfleet changes the scale between ENT and for TOS too).