When I first looked at Malmo and Hodgie's logs years ago, I couldn't figure out how they were so fast because I know several guys with PR's around low/mid 14:00, high 29:00, 2:18-2:21 who train just as hard or harder - similar volume and workouts but they just aren't as fast and don't make gains as quickly or continue making gains as long. Not unsurprisingly, these guys trained similarly in HS as well, but ran 20 seconds slower for 2 miles.
Running, like every other physical sport, is largely dependent on genetic endowment. No noe would hesitate to assert this is true of sprinting and weight lifting, so why do we refuse to see it is true in distance running? Probably because the work is so hard and unforgiving that the people who find their way into running often do so for psychological reasons rather than physical ones - not many people without talent are going to plug away at sprinting because it doesn't offer the many intangible awards of merely participating at whatever level.
Let's take 2 young high school kids:
Say a guy who is "untalented" and a guy who is "talented" who both have no background lifting weights decide they are going to see how much they can bench at the end of a year lifting 3 times a week, together, every day. On the first day of lifting, they both start with the same weight 120 pounds and each do 5 sets of reps to failure. Talented Guy does 10,9,8,7,5 and Untalented Guy does 9,7,6,5,3. So talented guy is somewhat better out of the box, but not too much better. But even worse, they continue to do the same workout every week - 5 sets to failure at 120 pounds - and by the end of the year, Talented Guy can then do 25,23,21,20,19 and Untalented Guy can do 18,16,15,14,12. Untalented guy has literally demonstrated Malmo's dictum - he has gotten considerably better, but untalented guy has worked just as hard as talented guy and now lags even further behind him than he did at the start. Untalented guy has worked just as hard as talented guy (he did his 5 sets to failure every session just like talented guy did), but Malmo would seem to deride his mediocrity as not being a hard enough worker even though he has done the same workout as talented guy every session for a year - he just didn't improve as fast or make as big gains. So Untalented Guy is in the unenviable position of KNOWING he works as hard as the other guy, but having his lack of parity chalked up to not working as hard.
To make the example even more real world, Talented Guy starts adding an even greater workload and continues to improve while Untalented Guy, frustrated by his lack of parity, decides to work harder and makes no further gains.