I think that's not what he wanted to ask. He's asking whether or not those exchange are trading "real" coins and have the assets to back it up, or just arbitrary ticker.

IMO everything is verifiable on the blockchain, which is why some bot like Whale Alert can label an address as "Kucoin Hot Wallet", "Binance Cold Wallet", etc. On top of that, as long as you can still withdraw your coins from that exchange I think that's fine. If you still feel nervous while you do that, then use DEX or make P2P deals.