By the book
The following is from the controller’s handbook (Section 5-9-1) and provides guidance to a controller when vectoring aircraft to the final approach course:

“Except (for visual approaches), vector arriving aircraft to intercept the final approach course:

a. At least 2 miles outside the approach gate, unless one of the following exists:
1. When the reported ceiling is at least 500 feet above the MVA/MIA and the visibility is at least 3 miles (report may be a PIREP if no weather is reported for the airport), aircraft may be vectored to intercept the final approach course closer than 2 miles outside the approach gate but no closer than the approach gate.
2. If specifically requested by the pilot, aircraft may be vectored to intercept the final approach course inside the approach gate but no closer than the final approach fix.

b. For a precision approach, at an altitude not above the glideslope/glidepath or below the minimum glideslope intercept altitude specified on the approach procedure chart.

c. For a non-precision approach, at an altitude which will allow descent in accordance with the published procedure.”

The controller’s handbook also contains a table that limits the final vector intercept angle to 30 degrees, unless the vector is to a point on final less than two miles from the approach gate, in which case the maximum intercept angle is 20 degrees. The important number to remember is 30 degrees, which is the normal limit. This is why the controller can cut the corner on the intermediate segment, because he/she is (hopefully) lining you up at a lesser angle and at a more precise position than can be achieved with non-radar segments of the IAP.