I remember a discussion with at least PJ, Charlie and me, where PJ mentioned his athletes not wanting to run hills without adequate warmup facility.
I happen to have the near perfect situation for either. I live literally down the hill from one of the top high school track/xc programs in the USA. There is a rekortan outdoor track within about 30 meters of a steep hill somewhere around a 40 degree angle. It is paved but perfectly flat.
There are two grass areas available. One is field turf, which I know Charlie is not in favor of. There other is at the top of the hill and maybe another 50 meters away. It is large enough to run 300s and such on the grass just like the Jamaicans, but the grass is cut higher than shown in the Jamaican photos.
So, I think I prefer to stick with 10X40m up the steep hill, which is one of the MVP workouts.
At this point, I don’t see a reason to not do 10X40 twice a week and 300-450 twice a week for GPP.