There are a few theorys out there some of them ancedotal and others in the realls of engineering design.
Rumours out there.
1. When they produced the first 3 pre production machines they had a different landing gear design and were quite nice to land. The RAF took one look at it and said we would prefer the extra traffic load . And they replaced them with straight legged with about 4" of travel. Then the fun began.
2. The wing on full flap has a nonlinear responce (I didn't have clue either what that meant) but apparently the air dams up behind the flaps at high alphas in ground effect and then something technical happens and you suddenly loose quite a bit of lift. This might have a grain of truth because if you float its going to suddenly drop you.
3. Its a JSP something or other design spec which is a military spec not a civi one (I think thats crap because other transport military machines don't seem to have the same issues)
4. Because of only having 1 wheel on each main leg the plane gets pulled down to the ground when they touch the runway and the friction spins the wheel up. This in my experence has some merit as a smooth landing is more likely with about 10 knts of crosswind, the runway deiced, snow packed or wet. No wind dry day I have thumped in some peachers which you wouldn't be able to spot the differnce in what I am doing to when I have done a greaser.
In practise experence counts alot but even then some pilots out there never really get a consistant pleasant landing and even what we would count as pleasant is somewhat firm.
When you first start flying them you get alot of crunchers and then they get better then worse again. Some folk get the nack and get predominately normal landings but even then occassionally she will bite and dump you on the deck for no apparent reason.
Also the props are extremely draggie at flight idle depending on how they are set up. If they are set low and you are still a couple of feet off the deck and you bring them back to idle unless you time the flare perfectly as she stops flying that 4" of gear travel doesn't soak up much.
The controls if you don't keep her trimmed right can get extremely heavy especially in high crosswinds and most of them only have a manual trim wheel. And it has a stupid spring thing thats meant to coordinate turns but you have to fight against it for cross controls.
Everone has a play with falp 20 landings and in my experence it makes sod all difference and just makes the rollout more challanging because the flap 70 lift dump doesn't deploy.
The J41 has different gear only has flap 20 instead of flap 35 has much more air over the wing at flight idle. And is much much more predicatable if you get the numbers right.