Watching this photo I see a puffy pillow that maybe leans on thigh of the shooter, but I don't see a shooter that leans with the thigh on the pillow, because in this case the pillow should be crushed like it is below the shin, while under the thigh is swollen with no sign of crushing.
If the aim is a general rejuvenation of field target shooters, then I think to forbid placing a support under the shin is a good way to go.
Otherwise I think it is just a way to make this sport more disagreeable, painful and penalizing for some, with the logical consequences. Practising field target is not obligatory as paying taxes.
If the problem is the cushion that rests on the thigh of the shooter, I think that is enough prohibit this from happening.
"the cushion can not touch the thigh of the shooter"
I liked the field target as it has been so far, I should be sorry if it change.
I apologize for intrusion.