Have you ever spent a decent period of time (>3 months) being immersed in another language? When you do it becomes clear that there is a language component to your thoughts, even if you don’t think in words.

My personal experience is similar to GP. My thoughts are very non-linear a jumble of images, emotions, sensations, sounds, colors, and intuitions. Organization into anything resembling a coherent sentence takes conscious effort.

But there are words mixed into that jumble somewhere, and I experienced a tipping point during language immersion / acquisition where I realized those words were no longer in my native tongue. It was around the time I started dreaming in the other language.