I was under the impression that the system was changed slightly in H3, just that you could set the limits to create a de facto infinite amount. Essentially a hybrid of the regular weapon spawns and power weapon spawns in H2.
Halo 3's system was you could enforce a minimum to exist on the map (carried or sitting on the ground at one time) and a max runtime (how many could exist at all). Max runtime was the limit the engine would ultimately spawn, which theoretically existed in Halo 1 and 2 because performance. Max runtime also counts against your Forge budget for that reason, so a max runtime of 1 costs you less than a max runtime of 12. When people would ask me to help them get some budget back, the first thing I did was go and lower a bunch of the max runtimes for various weapons and they'd magically get 500-1000$ back with no change to how their map played.
SIDENOTE: the engine has max runtimes for vehicles too, which it usually enforces. Except for Desolation, which has a broken version of this, so you can spawn endless vehicles.