Hi John,
Here is an extract from an EU-OPS Airline's Operations Manual:
P-RNAV/RNP STARs and RNAV Approaches may utilise specific phrases which identify the method of intercept, navigation, climb or descent to be used. Details will be published on relevant approach charts. ATC must be advised of any deterioration or failure of navigation equipment below that required for entry into a scheduled navigation area or continued operation in such airspace.
Vectoring and Positioning
ATC tactical interventions in the terminal area may include radar headings, ‘direct to’ clearances which bypass the initial legs of an approach, interceptions of an initial or intermediate segments of an approach or the insertion of additional waypoints loaded from the data base. In complying with ATC instructions, the flight crew should be aware of the implications for the navigation system.
‘Direct to’ clearances may be accepted to the Intermediate Fix (IF) provided that it is clear to the crew that the aircraft will be established on the final approach track at least 2 miles from the FAF.
‘Direct to’ clearance to FAF is not acceptable. Modifying the procedure to intercept the final approach course prior to the FAF is acceptable for radar vectored arrivals or at other times with ATC approval.
The final approach trajectory should be intercepted no later than the FAF in order for the aircraft to be correctly established on the final approach course before starting the descent (to ensure terrain and obstacle clearance).
‘Direct to’ clearances to a fix that immediately precede an RF leg are not permitted.
For parallel offset operations enroute (in RNP 4), transitions to and from the offset track should maintain an intercept angle of between 30 and 45° unless specified otherwise by ATC.
So it appears that the 2nm segment that you refer to does not necessarily have to be level flight but should be aligned with the FAT.
As Right Way Up said, vectors should be given either to the IAF or to a point at least 2nm prior to the FAF.
Another option that I have seen is to be vectored onto an intercept heading and then told to intercept the final approach course. Again, this intercept point is at least 2nm prior to the FAF.