Ask your lawyer.
We had an estate plan prepared by an law firm that specializes in serving elder law and it includes an AB Trust. The Trust is the beneficiary; if the specific investment/property title does not list the trust as the primary beneficiary it is not within the trust.
Our trust, and I think this is common to all AB (above ground/below ground) trusts, is such that upon the first death of I or my wife, the survivor can disclaim the what he/she inherits and pass it directly to the secondary beneficiary, which is our children. Thus the children do not have to wait until the death of both of us. With an IRA the investment can then be extended over the life of their adult life expectancy.
But my first sentence is the key; ask you lawyer in your state!
Ray