It's been a long time and I don't know the specifics of Silver's AI, but I don't think the addition of Synthesis really changes much? All it does is waste your time, and you tend to fight Silver in places that don't drain your resources that much (e.g. trying to exit Azalea almost assuredly after you healed) so you shouldn't be scarce on Ice Fang PP. Yes I know you won't have Ice Fang at Azalea but you get my point. If he tries to Poison stall for some reason you probably have a chance to 2HKO for free. Plus there's a fight or two where his Bayleef has Magical Leaf instead of Razor Leaf and that's arguably less threatening since no increased crit rate. Reflect matters more, but Synthesis might benefit you here if the AI uses it (again idk if that will happen) to heal and waste screens turns.Ironically despite Chiko being worse for the player to use compared to GSC, it is much more dangerous to fight Silver's Bayleef as Totodile/Croconaw due to screens and Synthesis spam.
Oh yeah the Sprout Tower is also worse for Chikorita in HGSS cause the Elder's Hoothoot has a Peck for Flying STAB now!Toto line also has to deal with a mandatory Bellsprout Tower, so it's no longer the juggernaut like GSC Toto, which is why HGSS runs use Cynda mainly before getting early Raikou with
And mandatory Sprout Tower does suck for Totodile, but that's only one small early roadbump compared to the highway of potholes Chikorita has to deal with.

