Pokémon RBY what is happening in these cartridge game clips?

[lord of the crabs]

This is confusing to me and this forum has a lot of RBY experts so I was hoping that someone in here knows.

Take a look at this clip at 37mins 05 seconds in
Dugtrios Dig does super effective dmg VS Vileplume. So I was thinking that maybe his emulator is working incorrectly?

So I found another clip from some other guy uploaded 9 years ago and in his video at 3:00 you can see Dugtrios Dig hitting Bulbasaur for super effective dmg.
Is it a bug regarding Dig, Dugtrio, or earth moves VS grass/poison types or what?

 

[HSOWA]

It's a visual glitch ingame: List of glitches in Generation I - Bulbapedia, the community-driven Pokémon encyclopedia

 

[lord of the crabs]

It's a visual glitch ingame: List of glitches in Generation I - Bulbapedia, the community-driven Pokémon encyclopedia

Ah tyvm, very interesting.