Two identical screws with different thread chamfers.

Your "fully threaded" (no chamfer) part is, in general, cheaper to manufacture than a "chamfered" part. A wide variety of part lengths can be made in a single, readily-made, relatively inexpensive "straight hole" heading die. A chamfered point requires either a more complicated/expensive die with a "header point" (this feature also typically limits the die's use to a single fastener length), or a secondary "pointing" operation prior to thread rolling.

If you require a point chamfer for commercial fasteners it is a very good idea to explicitly specify (and define) it up front. Point chamfer requirements/options will depend on the specification (if any) that parts are manufactured/purchased to.

I believe you're looking at manufacturer's discretion. E.g., the first spec. I checked, which I assumed to be more or less typical, specifes a maximum chamfer of 1.25 threads, but does not specify a minimum, which means it can be far less.