PDW = Personal Defense Weapon. I guess it is a new term.
As a civilian / commercial term it goes back to at least 2004 and the marketing of ACS HEZI SM-1.
As a military term it goes back a lot farther and the M-1 carbine was functionally a "PDW" given how it was issued and employed.
The Israelis required there personnel to carry a persona defense weapon and as such it applied to reasonably small and portable weapons like the Uzi, MP5, Colt 9mm carbines and the shorter M16 variants like the XM-177.
Today, militarily speaking a "modern" PDW is by definition a "compact automatic weapon that can defeat enemy body armor, can be used conveniently by non-combatant and support troops and as a close quarters battle weapon for special operations and counter-terrorist organizations." In effect as body armor has become much more prevalent they modified the term to address the need to defeat at least soft body armor.
That revision in the 1980s was the basis for the 7.7x28mm round and weapons like the FN P90, among other developments.
But in an armed citizen, home defense context where body armor is not normally a factor the old defintion still works just fine.
So...no. It's not a new term at all. Even for civilian marketing purposes it still over 20 years old.
And its a lot smarter to be using a term like "personal defense weapon" than it is to use "assault rifle", "military style rifle", "military grade rifle" or "mil-spec rifle".
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As a home dense concept an AP5 or similar firearm makes a great deal of sense. An AP5 SBR for example is short, handles well, is very reliable, is easy to suppress, and looks intimidating to a potential home invader.
It's also in line with the PDW concept in that its easy to use an easy to shoot accurately by persons with limited training.
I'm not really seeing a downside.