I agree this is a much more reasonable statement. The argument here would be on "what is reasonable bounds", but I think this statement focuses on the understanding that balance is not "rigid" or "perfect", that it is a range.....and a game that is falling within that range must be considered balanced.
Now as to whether 5e falls within that "reasonable bound", we all of course have our table experiences to draw from. For example, I will use one of mine. Probably the closest I ever got to "truly pushing my party" was when they faced:
Party: Six 9th level PCs + one 11th level NPC cleric vs 100 githyanki archers, 10 githyanki knights, 3 githyanki battle skiffs, 1 battle barge, 1 githyanki general + 1 githyanki battle commander. Ballpark CR was 30 all said and done (and my numbers are probably a bit off I ran this about a year ago, especially the archer numbers I just remember it was quite a lot of them).