Is falling on your butt a "purposeful threading of movement?" Is it "necessary to the whole?" Does it serve an "underlying vision?"
Usually not. In rare cases a skater can manage to stay "in character" after a fall and continue performing the program with no real disruption. But 99% of the time, there's at least a second or two of disruption.
Well, I guess finishing your highlight element with a splat is "finding a conclusion." But it greatly detracts from building energy, easy flow into the next phrase, etc. When a skater has multiple falls he has not carried out the intent or the details of his choreography. He should not get choreo marks in the eights or nines.
The original PCS guidelines advised judges consider what percentage of the program met the criteria for each component. 100% of the time would be worth 10.0, 90% would be worth 9.0, etc.
There is a problem with that approach for other reasons -- e.g., it would be possible to meet the criteria just adequately throughout the program, whereas someone else might meet them exceptionally well for 90% of the program and not at all for the other 10%. So who would deserve a higher score for that component?
But even simplifying to look just at percentage of time, a 4- or 4 1/2 minute program is 240 or 270 seconds.
Let's say the average fall disrupts the program for 3 seconds.
If the rest of the program meets all the choreography criteria for the entire rest of the program, then a senior skater who is otherwise deserving of 10.0 for the rest of the program could easily deserve to still stay in the 9s just going only by percentage of time.
If the skater gets up and is back in the program immediately afterward, that's not much of a disruption.
If the skater has moved on but the viewer is still thinking
"Oh no, she fell! How many points will that lose? She'll never win now! There go her chances to qualify for (Worlds, Grand Prix Final, third spot for next year, etc.) Thank goodness I have a clean copy of the program from [earlier competition] that I can rewatch when I just want to enjoy the program"
or
"Wow, he fell! Bwahaha! Now my favorite actually has a chance to win after all, if only the judges will penalize that fall enough. They'd better, but I know those judges' tricks. They'll probably hold him up as usual..."
Well, those thoughts may last a lot longer than 3 seconds and disrupt the viewer's aesthetic experience of the program. But most of that disruption is happening inside the viewer's head, not in what the skater is doing on the ice.
Of course, most skaters don't start out close to 10.0 or even 9.0 to begin with, because the quality of how they meet the criteria is not topnotch or because they waver in and out of meeting them while busy concentrating on setting up elements. But if they lose only 5% of their the potential time doing good stuff to falls and recovery, why should we expect their PCS to drop by more than 5%?
This is a problem that could be addressed without any rule changes at all.
Yes, without any outright rule changes the technical committees could issue guidelines encouraging judges to penalize more for falls in the PCS. And even without such official guidelines, individual judges could decide to do so on their own and could discuss their reasoning with other judges and maybe convince them to do the same.
But I still don't think you're going to see a couple of breaks of a couple seconds each leading to penalties worth 10% or more of the PCS as a whole. That's not how the PCS are designed.