The cheek and rear mounted radars do seem a little odd. They could only be effective against 4th gen type targets at pretty close ranges, like WVR, and against a 5th gen it seems they would be useless. The jammer explanation does make more sense, perhaps with a secondary detection capability for missiles and aircraft that get behind the fighter. Basically fulfilling the role of DAS on F-35, only with an active emitter.
One of main purposes of the cheek arrays is to expand coverage of the main forward array. Phased array radars give their full range only straight ahead, steering the beam off from centre axis costs them range. This in contrast to mechanically steered antennas, which can employ their full range over much wider area.
One solution for this is to make mechanically steered phased array, this is used in for example Eurofighter and Su-35. Another is to add more arrays which can be combined with main array to produce more powerful off-axis beams. F-22 was supposed to have cheek arrays but they were cut for cost reasons.
Also, modern AESA radars are no longer so much 'radars' as part of the multipurpose electromagnetic sensor/emitter system. They can be used to enhance EW and IFF capabilities, and to some extent act as missile approach warning sensors.