Yeah, but the question is are they stating what labeled tire size should fit or what actual tire size will fit? Those can be significantly different and manufacturers are taking different approaches.
The conservative method is to say 700x48 (labeled size) fits but have good clearance for an actual tire width of 51 mm because some tires run big and wide rims make them even wider. The legal team may insist on that approach for liability reasons.
The engineering mindset is to say that the user should use tires that measure 51 mm or less. But that nuance may get lost in the chain of documentation, marketing, press coverage, forums and user understanding. So then someone may run a 50c tire (actual width maybe 54) and have a rock get stuck or mud wear thru the frame.
It’s unfortunate, but there’s not standardization in reporting frame tire clearance. Plus most people think 48c = 48mm.