AS far as I know, Trust Wallet 'internal' exchange is DEXes that operate on a network. You can't exchange coins from multiple chains easily there unless you switch your Bitcoin/ETH/etc to a pegged token on that chain. I usually use their instant exchange feature to exchange coins from the BNB chain, while for BTC and other major altcoins, I'd use another exchange to do that.

The lesser degree of convenience compared to if you store your funds in exchange is worth it because you have more control over your funds. This means in case of an exchange hack or something like that, you still got your funds.