I can't really say I understand why people suggest this. Haven't flinds traditionally been basically the even nastier kindred of gnolls? I know for a fact that Pathfinder makes them into demonically-augmented "champions", born through selective breeding and the blessings of Lamashtu. Plus, in the podcast, I'm pretty sure Perkins outright states that he's taking them down the Pathfinder route and making them born champions of Yeenoghu - at the least, they're wielding triple-headed heavy flails in Yeenoghu's honor.
I mean, I certainly wouldn't complain if flinds were used as just "the gnolls who have renounced Yeenoghu", it's just... why do people think that's a thing that Volo's Guide will do?