PFs 17-24 belong to SER and being of more recent origin were built longer to berth 24 coach trains. PF nos. 1 to 14 are of the old vintage when 24-coach trains were not even dreamt off. Hence they are presently inadequate. But yes other than 9,12,14 and possibly 8, the others are too short for the purpose. BTW PFs 1 to 5 and often 6 are used by EMU locals with 9/12 coaches.
An interesting tidbit is that even about 10 years ago, KING COROMANDEL used to depart from the OLD COMPLEX (PF 14) but arrive at the NEW COMPLEX (PF 18 TO 21). Passengers often found this arrangement very confusing causing people to nearly miss the outgoing train. Fortunately, better...
more... sense prevailed and this anomaly was rectified.