I would say Sawyer still wins in a close match without Mega Evolution and wins pretty decisively with Mega Evolution.
Yeah honestly Metagross could've done the bulk of the damage to bring down Swellow since Swellow visibly didn't look tired/injured after beating Donphan. Aegislash pretty much have Pikachu mid difficulty(though Pikachu did take a bit of damage from Clawitzer- Electro Ball/Dragon Pulse clash)
I wouldn't say bulk but it wasn't insignificant. I feel like with Tyson's Sceptile there are 2 interpretations. 1 is that Sceptile = Glalie = mid t-2 since they both KOed each other. The other is that Sceptile would be slightly above Glalie (high t-2) since it launched a neutral effective move but Glalie launched an SE move. Taking the high ball we get:
Slurpuff vs Shiftry -> Slurpuff
Slurpuff vs Donphan -> Donphan
Salamence vs Donphan -> Draw
Slaking vs Hariyama -> Slaking
Slaking vs Sceptile -> Sceptile
Clawitzer vs Sceptile -> Sceptile
Aegeslash vs Sceptile -> Aegeslash
Aegeslash vs Metagross -> Metagross
Sceptile vs Metagross -> Sceptile
Sceptile vs Meowth -> Meowth barely
with a low ball the changes would be:
Sceptile vs Clawitzer -> Draw
Aegeslash vs Metagross -> Metagross
Sceptile vs Metagross -> Sceptile
Sceptile vs Meowth -> Sceptile barely/Draw
Basically Aegeslash would bring Metagross down to like 15-20% in a regular battle but closer to 25% if chip damaged by T-Sceptile setting up an uphill battle for S-Sceptile. Now before Tyson supporters think I switched sides:
Mega Sceptile vs Meowth -> Mega Sceptile
Mega Sceptile vs Metagross -> Mega Sceptile
Mega Sceptile vs Sceptile -> Draw (high balling T-Sceptile here)
Slaking vs Hariyama -> Slaking
Slaking vs Donphan -> Donphan
Clawitzer vs Donphan -> Clawitzer
Clawitzer vs Shiftry -> Clawitzer
though Sawyer could be a real d*** and send Aegeslash after MS yielding:
Aegeslash vs Donphan -> Aegesalsh
Aegeslash vs Shiftry -> Aegeslash
Aegeslash vs Hariyama -> Aegeslash by default even if it were low on health
Y'know I keep hearing that Sawyer only did well because his strats were tailor made for Ash's team though honestly those strats could be applied against a plethora of other Pokémon and it's not like Sawyer doesn't make strats for other traienrs (like Tierno). Sawyer also has good improvisation skills like Ash (though of course not to the same degree) and his skills were good enough to earn praise from a Champion.