Oh, it's been a persistent claim since the days of 3.5 at least if not earlier. 4e was where it really got blatant and widespread though...and the irony of course is that the text explicitly tells you not to do that, and rather tells you to give mixes of challenges from easy (e.g. roughly level-4) to very hard (e.g. roughly level+5, maybe level+7 if you're feeling particularly spicy). Many, many, many people tried to spin its (very effective) XP budget rules as mandating perfect lockstep encounter levels, or (hilariously) claiming that it worked like Skyrim where every encounter would automatically level up to match the party no matter what!
The 4e era was full of some really choice strawmen.