Actually the default value of the final argument is true - i.e. look for value or next value smaller (assume sorted lookup). So taking the value out is the same as 1 is the same as true - i.e. doesn't work.

Excel "encourages" the user towards sorted arrays and range_lookup = true (which we might perceive as more obfuscated) as the function operates much faster that way (how fast depends very much on the order of the data). I, personally, very rarely find the increase in speed to be worth the ambiguity/fussiness of the function with range_lookup = true, but perhaps I'm lazy...?

CC