Vent Blowing Cool Air at Higher Temps or Just Me?

Sorry for bumping another old post/thread (newbie search and post!)

I have been driving a 19 year old truck for the past 19 years and it's a simple cable driven blending door. You turn the dial to set the desired output air temp.

So when I bought this Prius last week and set it to 68 degrees (it was very cold in the cabin) it was blowing really hot air out. I was like, "dayum, wth?" Then today, it's much warmer outside with the sun baking the cabin, and I could turn it all the way up to 77 degrees and it was still blowing cool air out... same air temp if I had it set to 67 degrees.

So thank you for confirming what I was hypothesizing.

My question: Where is the temp sensor in the cabin that dictates the climate control?