In a Michigan Trust document, what does "free of trust" mean?

Location: Michigan, US. My Mom died and I finally got a copy of the Trust and Will. In the Trust, it states her home is to go solely to my sister "free of trust." (My sister and I are the only heirs.) Why would an attorney write that? If it's "free of trust," doesn't that mean it's open to probate - and then I could petition Probate Court for half of it?

Facts: 1- Mom did not need a Trust. All she had was her home and bank accounts, totaling less than $300K. 2- My sister has hated me since I was born and has never grown out of it (she's now 62yo), thus she does not communicate with me. She refused to give me a copy of the trust until her attorney did so. 3- We (rest of he family) now know there was elder financial abuse (sums of money regularly taken from Mom's bank accounts) and we suspect elder emotional/mental abuse (threatening to not take care of Mom unless Mom did what sister wanted). 4- I've asked another atty, but he thinks it's a circular argument - there's a document that puts the house into the Trust upon death, so if "free of trust" takes it out, then he goes back to the document that puts the house into the Trust upon death, thus avoiding probate. Whereas, I think it's a linear argument and the house goes from the Trust and then open to Probate. 5- I worked in the Financial Services industry, including working for a Trust Dept. of a bank, but I have never seen this phrase used (but I worked in another state, not Michigan).