Based on my admittedly lacking of understanding of the game spawn systems, there are two systems in place that control monster generation. There’s regular map spawns (which are simply timer based) and what’s called internally as ‘smartgen’.
Smartgen is a neat system that ties monster spawn to player presence, and does things like spawn monsters around a player and sets ambushes and such. If you’re walking around and monsters pop up randomly and attack you, that’s smartgen. This system is independent of normal map spawns, so that’s why you’ll still see mobs spawn sometimes between the fixed spawn intervals. Smartgen has a kind of internal counter that ticks up as you do stuff and when it hits a certain point, it activates and makes mobs for you. What they did is they halved the level needed to trigger smartgen, so you should reasonably notice more monsters popping up around you.
Trouble is, not all mobs use smartgen… actually a lot of the mobs that actually matter, like the oft-cited Egnome spawn, Glizardons, etc, don’t use it. So this change won’t actually make a difference in those cases, the ones people were actually complaining about.