It must depend on the fit of the liner through the neck/chest, because there is no way I could use the Horseware liners on my warmblood without attaching them at the neck - they would end up extremely twisted. The Rambo turnout (with the v-clip front) is a great fit through the neckline and chest and doesn’t move, but the chest strap of the liner is set way too low for my horse, and allows the front to twist sideways very easily if it’s not attached. I ended up sewing on an extra plastic clip above the velcro closure on the liner, because even attached at the neck it still moved around a little bit. That mostly solved the problem but I still wouldn’t use the liner without attaching it to the turnout rug at the neck to keep it stable.
(I have different weights in the liners and the turnout rug and liners are all labelled as 84 inch).