I didn't forget, it's Just because when Ash was with Heracross in hands he didn't make the whole Jotho team, It was still mixed with kanto, so I didn't put Heracross because I couldn't say especifically that Phanpy took Heracross's slot...
Just like, we didn't have: Pikachu/Totodile/Chikorita/Noctowl/ Cyndaquil/ Heracross (Bug/fighting) for later Heracross's sixth slot to be replaced with Phanpy (ground)
The truth is that in Jotho, Bulbasaur kinda took the sixth slot through fourth Season and a little bit of fifth, maybe we could consider him the Poison type in the sixth slot, that ocasionally after some episodes left to be lab leader, Ash gained Phanpy's egg, so clearly Bulbasaur It was taking a pseudo sixth slot, since he's not a Jotho native.
Believe in me , All Pokémon I didn't mention is because It was unacessary to the pattern explanation.
While you brought a great point really interesting, about fighting type;
If we consider the 8 generations, we can say that he didn't fulfill grass type slot in 2 generations , fire in 1 generation and water in One generation.
But fighting Just like grass we didn't have in generation 3 and 7, and if we can consider that possible "fighting slot" we'll have:
Gen 1: Primeape
Gen 2: Heracross
Gen 3: ??????
Gen 4: Infernape """"sharing fire slot"""""
Gen 5: Scraggy
Gen 6: Howlucha
Gen 7: ?????????
Gen 8: Lucario/ Sirfetch'd
So If we consider Infernape for fighting slot, and Talonflame for flying avian slot, se won't have a fire type representative for gen 4, 6, 8
If we consider Talonflame and Infernape for fire slot, we won't have a fire representative for gen 8 only, but also we won't have a flying avian representative for gen 6,7 and 8 and won't have a fighting representative for gen 3,4 and 7.
If we consider the repetition of types only, we didn't have fighting type for 2 generations Just like grass type and flying type avians.
Concluding that If it's about repetition of types through all 8 generations, fighting types could be a pattern Just like grass or flying (avians) type.
But remember that in the pattern I mentioned It was till generation 5, when a sixth fighting type slot never happened in generations 3 and 4, different from the other 5 types that repeated without missing even when Ash didn't get a starter.
Water slot: Greninja
Fire slot: Talonflame
Fighting slot: Hawlucha
Dragon slot: Goodra
Flying slot: Noivern