Don't know how you ride the proneboard but it must be really intense for a board to show any signs of mushiness or lack of energy transfer as you describe in 6 months.
I know we do not pump the wing boards much but i ride fast through chop,do millions of S-turns,DW, maneuvers etc...
In the last two years i have winged a lot, i do not think anybody can spend as much time on foil prone surfing for 6 months as i have winged in those two years.
If the construction was as bad as you say my Naish Hover Ultra should be falling to pieces,but it is good as new.None of the symptoms you describe.I just checked.
I watch all the Insta ripper vids and prone surfing is getting more aggressive every day but 90% is pretty mellow riding even at the top level.
As for the pumping, it is a very repetitive load but not that big, have no way to measure it but i do not think it is bigger than an upwind wingfoil run through 18kt chop.And wingfoil boards have a lot more inertia than prones.
www.instagram.com/p/CU8xaceDjVG/?utm_medium=copy_linkNot doubting your what you posted,if you say your boards degrade in 6months i believe you,but it does not fit my experience at all.