could be wrong, but I think what Medicineman is talking about is that the PPP bonus doesn't add to the FFBA and then gets halved for encumbrance.
No

What I'm writing about is that FFBA has the bonus that you add only half the Encumberance to other armor
f.E. FF 1/2Body is 4/1 Armor Jacket is 8/6
Both together have an encumberance of a 10/6 Armor
This Bonus of 1/2 Encumberance is due to the Factor that the Armor is exrtremely flexible and Taylor made
but If You add rigid Armor Plates the FF BA isn't flexible anymore
You Could add PPP to FFBA shure
F. Example the PPP Helmet is +0/+2 a Suspensorium is +1/+1
If You add this to FFBA 6/2 you get a 7/5 armor
but this Armor won't/shouldn't get the 1/2Encumberance Bonus if added with another Armor
It would be perfectly Ok (ImO) If you have a FFBA and other armor (Armored Jacket f.E. ) that you add the PPP to the Armor Jacket
but it sounds like he's trying to say that if you put the PPP directly on FFBA then you losing the 'halving effect',
Yes thats correct

thats why I add the PPP always with the other Armor
My Chars often wear 2 different Armors, one being FFBA and the other a different one and If its not encumbering I might add a piece or two of PPP to the other Armor
With another quite flexible Dance
Medicineman