Paraphrasing the rulebook (I don't have it close at hand), FNP is allowed against attacks that lacks the following abilities:
AP1/2
Monstrous creature close combat attacks
Power weapons (including fists)
Instant kill
Succesfull rending (getting that 6 to wound)
anythign that states "armour saves are never allowed".
If ti was that you weren't allowed FNP if the shot goes through your armour, Ork Painboys would be seriously rotten, what with Nobs (who they accompany) only having 6+ Armour...
This is correct, however he stated "a model with T5". Think an Ork Warboss or something.(also, they have only T4(5), so an S9 shot would instant-kill them anyway)