I know that it is an extremely ambitious date - but that is part of the strategy (as JFK said about the moon programme).
I also know that we (armchair experts?) think things are easier than is actually the case but it is worth remembering that the first "spade in the ground" for the MML bridge was Feb 2016 - only just over 3 years ago. Foundations started in Jan 2017.....since then that bridge has been finished, the Canal bridge is halfway completed and much paperwork and planning has been done for the remainder.
The embankment section to the North of the MML bridge could have the earth moved quite quickly - it was moved from the paddock in about a week. Because it is higher and closer to the brook, there may be some pilings required along the Eastern base? Then a point on the chord line, ballast and track over the MML bridge, pose steam engine on bridge - excellent publicity and increased project momentum.
Track over the canal bridge, pose steam engine over canal - excellent publicity and increased project momentum.
Build arches and abutments over Preci-Spark car park and tip road, lay track, pose steam locomotive on arches, excellent publicity increased project momentum.
Build the 400m embankment, lay track........... Gap Bridged!
There may well be later changes to extend the double track along the embankment - both at the South and at the North over the A6 bridge, there will be more alterations to trackwork and signals North of Loughborough station, there may well only be the single track initially past/through the engine shed.......But the Gap will have been filled..... by the end of 2023.
That is the vision for the 50th Anniversary year.