conuly

No, they're not.

Ch is - in any dialect - an affricate. It's a combination of the stop t and the fricative sh. (This isn't IPA, just bear with me here.) With me so far?

When saying words like train and tree, it's easier if you... oh, I forget the word. If you insert a sound between the t and the r, because they're made in different parts of the mouth. The sound easiest to put there is a sh. Ch-ree. People do that all the time. When it comes to tr-, though, most people don't "hear" it, in the same way that they don't hear that the ay in say is actually a diphthong.