Trimmed length has nothing to do with head space of the brass to your chamber. Let me elaborate a bit here.
The maximum case length as determined by SAAMI spec is about the length of the neck. If a case exceeds the max. SAAMI length, what can happen is, when it has a bullet seated in it, is chambered and fired, the mouth extends to far into the throat, and when the cartridge is fired the mouth must be able to expand to release the bullet. If the neck is too long, it becomes pinched, the result can be extreme pressures, very extreme. This is the entire reason for SAAMI spec relating to trim too lengths, and maximum case length. Although a case that is in need of trimming may easily chamber in multiple rifles, it may not be safe to be fired if it exceeds the max length. This particular element of reloading is completely, and totally controlled by trimming and unrelated to resizing.
Head space of the brass, which is the distance from the case head, to the shoulder in relation to the dimensions of the rifle, from bolt face to shoulder datum. This is what effects cartridge fit in a particular rifle and is adjusted by how much one pushes / bumps the shoulder back during resizing, and it has absolutely nothing to do with brass trim length.
GS