As a regular cyclist the figures were imteresting, and realistic but I think missed a couple of important points:
Terrain, hilly terrain will slow you down, and make it harder work.
The one that everyone misses, wind. We live in an exposed area, and I regularly encounter head winds. Unlike hills, where you 'get back' what you put in head winds are more of a problem.
In simple terms wind resistance is proportional to the square of the wind velocity. So imagine a 10mph head wind, you ride into it for 1 mile at 10mph, the head wind is 20mph, so wind resistance is 4 times that on a still day, then return at 10mph where wind resistance is zero, basically wind restance losses have increased by a factor of two on the day with a 10mph wind against a still day for the return journey. (OK there are other factors at play as well)
There is also rain, snow and heat to consider, my own view is if I am riding to or from a station in all weathers, in normal clothes, with just a rainjacket or coat then 2 or so miles each way is about the limit if its a daily all weather ride, and even then there will be a few days where its not practical (e.g. ice and snow) so what is the fall back.
When you arrive at the station you then need secure cycle parking.
Cycling and rail travel can be a good way of expanding a rail catchment area, but currently there are a lot of barriers