As for Bug types hiding in winter, I guess that's good to ask. I mean, most of them have wings, even Heracross. But even bugs who don't have wings, means, maybe they are cold blooded. I mean, not all bugs are warm blooded.
As for water not being weak to poison is an interesting one. To consideration of my understanding of 2nd year high school biology, poiso can come in a variety of forms. Whether solid (Like poisonous plants/pokemon like Venusaur, Amoongus [D*** mushrooms!!!], and Roserade), Liquid (Tentacruel and, Hypothetically, Jellicent, Some Snakes like Arbok carry liquid poison by stinging/biting its prey), or Gas (think of today's factories or burnt fuel / coal. Not healthy).
Ground types being neutral to flying makes sense. Has there been Any Typhoon/Hurricane/Tornado be able to remove a piece of land away from the main land? Not really. Just the top layer of the soil only since it cannot remove the bedrock and that part of the outer crust above the bedrock
But Bug types attacks super effective against psychic. Wow! I never knew that the fear of bugs is one of the highest worldwide! I mean, I wanna ask you guys this. Can you eat a LIVING COCKROACH? (if you cannot, just give it to that one guy who had a Guiness World Record for being able to eat cockroaches ALIVE!) Me, Awww HHHEEEEEELLLL NNNOOOOOOO!