I cannot answer that for you in terms of Series X performance. On a PC, there certainly is a penalty. With the Xbox, though, it may already be capped performance-wise that it would perform the same at 1440p and 4K other than the visual differences.
EDIT: Let me add that some claim the Series X is running the sim at 1440p upscaled to 4K. I’ve not been able to find data that confirms this.