On a Generation I team, why did it let me put full Effort Values on every Pokemon?

Question

On Pokemon Online.

Answer 1

EVs in older games:

You could gain up to 65536 EVs in every stat (HP, Attack, Defense,
Special and Speed), so you didn't even need to consciously ‘EV train’
- you'd normally gain all EVs by the time you reach level 100.

Source: PokemonDB EV page