Trust Wallet is considered to be a non-custodial wallet but is closed source. Because of this, you can't really dig deeper to find out more about the wallet, which is why an open-source wallet is recommended for investors. I believe that the fact you have questions about Trust Wallet indicates you are not confident in it, based on what you have noticed or discovered about the wallet. I have heard some people complain about this particular wallet, which is something that can't be explained. A wallet performing in ways that can't be explained seems to be risky. With Trust Wallet, you have access and control over your keys, but since it is closed source, you don't have access to review the wallet.
Yes, upon checking, not all of their codes are open, so they are closed source. So we really don't know the functionally in the background. Although they might claim that there are no backdoors whatsoever, still we can't trust that kind of wallet.
Same with other hardware too, some of their codes are open, but some like the firmware and hardware wallet are closed and can't be validated by us. So we should avoid this kind of wallet as all cost.