I know 45min or 50min is some large % of an hour. At the same time, there is a reality to the power duration curve with people's physiology.
Part of this argument I feel some folks don't consider for racers and riders who are Cat 3 and "slower" is the nature of the distance of their races and the energy systems those folks typically use. They don't really have a use outside of a regional TT championship of 25mi to go all out for an hour. They need good 1min, sprint, 5min, 8min power. Totally different ratio of the energy systems used in the body. You can race successful crit and road as a 3 and slower likely not even ever doing an hour all out. I bet you could train some 3's without even ever having them do 2x20's and they do fine.
For a 20min test you're able to rely on your ability to nail some shorter 8min intervals. The next part of the whole "95%" or even "92%" or even "90%" of a 20 min test deal is that if you never hone the aerobic engine in that hour duration...........you get much past that 20min your power is falling like a rock as you near 45min and an hour. This is because you've built the foundation for power expenditure in the 1min thru 8min range, mostly. So you don't have the foundation at all for stuff beyond 20min.
I think the BEST bet for the largest group of people able to do this, starting at the lowest level of fitness..........would be competitive Ironman age-group athletes. Their training and racing pretty much centers around long duration. Their power duration curve probably looks crap from sprint to around 5min, then from 20min through 4hours is probably pretty darn flat. I'd put a nice beer bet on those dudes having the highest count of hour 300w achievers.
With track racing, I figure this is why you have amateurs doing 3km pursuit and elite doing 4km. The power and duration work out better for the body's energy system for the type of event they want. When I see folks doing 17min 10mi TT's, that's going to be a bit more power they can make in that 17min than if they had to go 25min like a lowly clubbie. 30w? 50w? Maybe even 75w? Going from 17min to 25min, that's a 50% longer race! That's almost not the same race at all!!!
This REALLY comes into play for running since your speed is pretty much perfectly linear to your "power". To me a 5k run race simply isn't the same measure for an elite running 17min or less where "joes" are doing 23 to 30min. Literally 50% longer a race for the "joes". This is really drastic with a half or full marathon. A pretty common goal for a recreation/fitness runner is to break 2 hours for a 1/2 marathon. That's like 9:15/mi. The current unofficial WR for a FULL marathon is now under 2 hours.
I bet this comes into play on those climbs also. Clubbies on Zwift take maybe up to 90min up Alpe du Zwift. I follow a domestic pro on Strava that lives near us that's done it in ~40min. Not even long enough to hit an hour.