As such my theory still stands that the game absolutely spawns aggressive entity’s near the player for no reason other than the passing of time.
I'm unsure what you mean by "aggressive entities" since all zombies/dogs/wolves/bears are aggressive, always. If you mean "always targeting me directly" then I think you are misunderstanding the AI behavior. But yes the game absolutely spawns all sorts of things due to no other reason than the passage of time (or, in the case of screamers, due to "heat" in the chunk). If the zombies see you up on top of your POI then they're going to come after you. Were you crouching? Did you have light sources near you (campfire, holding a torch)? Do you have Feral Sense enabled for your game (significantly increases zombies' ability to find you)? Were you downtown or out in a rural area (changes #, frequency, and difficulty of biome spawns)?
The game basically has four types of spawns outside of blood moon: POI, scouts/screamers, biome, and wandering hordes. Biome spawns are individual zombies spawned here and there all day and all night long (more/less difficult depending on which biome you're in, whether your downtown or rural, and whether it's day or night). Biome spawns spawn in as 'active', but not alerted or targeting the player unless they detect you. They'll just wander around.
Wandering hordes are small groups which will move as a unit towards a spot near the player. When they are spawned they aren't alerted to you or targeting you, but of course they are moving roughly right at you. With Feral Sense turned on, you might need to be pretty alert and quick to hide if you want to evade detection. If the spot they're trying to get to is within the bounds of your base, they might attack the base I suppose to try to get to their target location.
Scout/screamer spawns are generated due to "heat", and lots of what you do generates heat. Building, repairing, workbench/forge/chem/cooking, mining, torches, and definitely the firing of any firearm. You can press F8 twice to see the heat in the chunk you're in.
Everything you've described sounds normal I guess, and can be explained by either biome spawns or wandering hordes, especially if you're playing with Feral Sense.
You might want to temporarily try out
Boid's Stealth Logging, a small mod I made which will log into the console when zombies are targeting you vs. walking to a spot vs. investigating a distraction, etc. You may think "that horde obviously knew where I was and was targeting me", but the log will show otherwise until/unless they detect you. Do not use the mod for normal play - it writes to the log pretty frequently when zombies are around and may impact performance. Turn it on for one of your tests and watch what is happening to gain a better understanding. And post back here if you see something weird. (If you want to keep the mod around, but disabled, you can just rename "mod_info.xml" and the game will ignore it.)