I can clear up some of this. First of all, mr_pikachu, you're getting a term confused. DVs were the same thing as IVs; the RBYGSC version of EVs was just called Stat EXP. Also, I usually see "IVs" described as standing for Individual Values, because they are the only things that make an individual level-15 Machop encountered in the wild different from any other level-15 Machop encountered in the wild (well, they were until Advance Gen introduced Natures.)

As for stats growing in the PC...Phoenixsong, you're absolutely correct. See, here's the thing: in RBYGSC, stats are calculated from species, level, DVs, and Stat EXP, but the game doesn't bother recalculating every single time you gain Stat EXP. There are only two times the game will see fit to re-figure a pokémon's stats:

1) at level-up or evolution, and
2) when you withdraw a pokémon from the PC.

Since, when a pokémon reaches level 100, it can't level up any more, withdrawing it from the PC becomes the only way to get its stats refreshed. This makes the practice very important, so much so that it has been named "The Box Trick" in the greater Pokémon community. If you hear RBYGSC players talking about "The Box Trick", this is what they're talking about--some people don't even realize why their pokémon are getting stat boosts from being deposited and withdrawn, but it's really because the Stat EXP they'd collected was being applied.