To be honest I don't think it matters AS much for small dogs that stop growing before 1 year old.
I think it's important to define what you mean by "stop growing."
There's a important distinction between the time that puppies reach their full adult size versus the time it takes them to mature.
Their full frame means that they're not going to get any longer or taller, but it takes time for the rest of their body to catch up, and for them to fill out and mature in all respects.
Their "full adult size," and "maturity" are not the same things. Tango for example, continued to thicken up around his chest area, get that very pronounced tuck under his belly, a slight ruff of fur around his neck (he's double coated) and gain weight until he was 18 months old even though he never got any longer or taller once he reached about 9 months. But he went from 2.5 pounds to 3.5 pounds in that following 9 months. And he's not and never has been overweight.