There is most likely something they know that you do not know. You have used it before, does not mean that you can always trust them. You have no idea what may have transpired in the company from the time you used them last to the present date. The security warning also could also be an updated feature that Trust wallet has introduced, so it always be that they warned you if anything should happen, Just like the function of a disclaimer. Anyhow, just be sure to read it properly and be extra sure of ehat you are doing.