You have a strange idea about Monaco. The reality is that in Monaco there is the tradition to invest a lot of money in the race of 1500m, paying the best rabbits very much more than in any other DL.
The secret of the times in Monaco are the rabbits. When Silas, coming from 3'34" in Nairobi, won in 2010 in 3'29"27, Augustin Choge wanted to run under 3'30", and asked for a split of 2'47" at 1200m. Collins Cheboi, one of my athletes, was the pacer, and was not able to arrive till 1200m, but ran the first 1100m very fast (2'33"), and Augustin had the courage to attack, being alone with 8 meters of gap after 1200m. This was the ideal situation for Silas, who loves the progression when there is fast speed.
In 2011, nothing special : Silas won again in 3'30"47.
In 2012, Asbel Kiprop wanted his personal rabbit, and ran 3'28"88, becoming himself the pacer for Chepseba (3'29"77), Nick Willis (3'30"35) and Makhloufi (3'30"80).
In 2013, again a race organized for Asbel with 3 personal pacers : 3'27"72 for him, and of course PB for Mo (3'28"81), Caleb Ndiku (3'29"50) and Birgen (3'30"77).
In 2014, the fast pace for Asbel was the reason because of the best PB of Silas (3'27"64), with the greatest race ever with 7 athletes under 3'30".
Put in your mind that the performances depend on the pace, not on the track.
In the past, nobody of the best athletes ever had his PB in Monaco.
These are the best performances of El Guerrouj, Bernard Lagat and Noah Ngeny :
EL GUERROUJ :
3'26"00 Roma 1998
3'26"12 Bruxelles 2001
3'26"45 Zurich 1998
3'26"89 Zurich 2002
3'26"96 Rieti 2002
2'27"34 MONACO 2002
LAGAT :
2'26"34 Bruxelles 2001
3'27"40 Zurich 2004
3'27"91 MONACO 2002
NGENY :
3'28"12 Zurich 2000
3'28"54 Roma 1999
3'28"73 Sevilla 1999
3'28"84 Paris 1999
3'28"93 München 1999
3'29"19 Bruxelles 1999
3'29"79 MONACO 1999
3'30"34 MONACO 1998
So, it's not clear because you think the track of Monaco can be shorter.
And quit to have some Conspiracy about the tracks in the World where normally there are the best performances : THERE IS NO TRACK OUT OF THE REGULAR LENGTH OF 400m, in any big meeting of DL, World Challenge, and in any case meetings of high level.
The procedure for the homologation of a Track for international competitions is very accurate and complex : for example, it's not possible to have a difference in the level among the first and the 8th lane of more than 2 millimeters, and the machines used for checking these levels are advanced electronic implements with very high precision.
I repeat : the fact some track, such as Monaco, Doha or Rieti, are able to produce very fast races, is due to 3 main factors :
1) The best quality of the surface (for example, these 3 tracks have a Mondo surface very thick, able to give back high elastic thrust)
2) Optimal weather, with very dry air
3) Specific interest in these events, where the organizers invest more money than in other events in order to guarantee a very fast and even pace.