El guerrouj has 12:50. So Farah is better than 12:53 despite running it several times but El guerrouj potential isn't better than 12:50?
Also Kiprop has actually presented some really interesting cross country performances against some actual good competition, it's really no stretch to think that he could run a good 5km.
Don't simply assume that being fast at 800m and 1500m means that he sucks at 5km, I reckon he would be capable of 13 flat or somewhere close.