At least as relates to gnolls this is a bit of a false memory that seems to conflate essentials with original 4e.
4e from the start had heavily demonic gnolls. I remember that being a contentious point at the launch of 4e.
I remember the early 4e dragon articles from when they were free PDFs and 367 had one on playing gnolls and the first 4e one, Dragon 364, had one on the Demonomicon of Iggwilv for Yeenoghu both articles leaning in hard on the demonic bad guys characterization.
The fourth of the four gnoll statblocks in the 4e MM is the gnoll demonic scourge.
Here is the description from the original non-essentials MM:
GNOLLS ARE FERAL, DEMON-WORSHIPING MARAUDERS that kill, pillage, and destroy. They attack communities along the borderlands without warning and slaughter without mercy, all in the name of the demon lord Yeenoghu.
Gnoll Lore
A character knows the following information with a successful
Nature check.
DC 15: Gnolls are nomadic and rarely stay in one place for long. When gnolls attack and pillage a settlement, they leave nothing behind except razed buildings and gnawed corpses. Gnolls often decorate their armor and encampments with the bones of their victims. Impatient and unskilled artisans, they wear patchwork armor and wield weapons stolen from their victims.
DC 20: Gnolls don’t bargain or parley, and they can’t be bribed or reasoned with. Gnolls are often encountered with hyenas, which they keep as pets and hunting animals. They also work with demons.
DC 25: Gnolls detest physical labor and often use slaves to perform menial chores. The life of a slave in a gnoll camp is brutal and short. That said, slaves who show strength and savagery might be indoctrinated into the gnoll vanguard. Such creatures are usually broken in mind and spirit, having become as cruel and ruthless as their captors.
DC 30: As the mortal instruments of the demon lord Yeenoghu, who is called the Beast of Butchery and Ruler of Ruin, gnolls constantly perform atrocities. When not scouring the land in Yeenoghu’s name, gnolls fight among themselves and participate in rituals that involve acts of depravity and self-mutilation.