For those interested, I have just checked the screens of iPhone 7 and 8 side by side with the same settings (True Tone off, both set to auto-brightness in Accessibility). The screen of iPhone 8 appears noticeably dimmer (less bright) compared to the screen of iPhone 7.
	
		
			
		
		
	
				
			 
 
		 
 
		
 
 
		 
 
		 
 
		 
 
		 
 
		