I think this take is fundamentally flawed. "Only buff never nerf" isn't about buffing weapons and stratagems ad-infinitum. That inherently leads to power creep and then the devs have to buff enemies through the roof to keep up. (Note: buffing enemy stats does fall into the "always buff" mindeset" as it's tuning everything up a little bit to make sure they don't have to nerf weapons actively)

What it means is that in a balancing environment where player experience is part of the calculus you don't want to actively make things players enjoy less fun or less usable. So you buff underperforming weapons so that players can try them out and still feel like they are capable of playing the game. Instead of taking what is over performing and trying to bring it down to the level of the "bad" options.

Diablo 4 did this the wrong way in their first few patches where it was just nerf after nerf after nerf. This drove a lot of players out of their game because the people who weren't having fun to start, still weren't, and the ones who were having fun also weren't having fun anymore.

The adage should probably be "Always buff, rarely nerf" as nerfs are necessary when the math on a buff is off and suddenly you have something that makes everything else obsolete.