I have recently purchased Murder in Baldur's Gate, and downloaded the Monster Statistics supplement with the three-edition-stats for named NPC's (tough thugs, Flaming Fist Privates, etc). These reflect a way to stat the NPC's depending upon which edition of the game this module would be plugged into.
The module was released in 2013, a period during the 5e/Next playtest and well before the PHB for 5th edition was released.
I was not yet back into the game/hobby at that point, and missed the playtest, so I have no point of reference on this.
Was Murder in Baldurs's Gate official D&D next playtest material, or was it issued/published for another purpose?1
1Besides the obvious desire to sell a product and earn revenue.