Don't be sorry ;-)

I just did some digging to find that Haswell does not imply extmodel 4, and in fact I've seen examples of the i5-4670K with an extmodel 1 through 4.  I think that 4 simply denotes the latest breed present in the latest range of MacBook Pros.  I could be wrong of course - like you I'm no expert - but I'm not seeing anything that specifically implies that Haswell = extmodel 4.