Rubbish. All of it. Kerr doesn't train to peak indoors. Most top northern hemisphere runners will compete indoors over the winter. That includes Jakob - when he isn't injured. Indoors must matter enough to him that has two wrs on the surface. Indoor tracks are slower because they are far shorter than outdoor tracks which is why all indoor records are slower than outdoor records and always have been.
The 1500 (held by Jakob) and mile wrs are over 4 seconds slower than the outdoor records. That suggests that Kerr's indoor 2 mile record is easily comparable to Jakob's outdoor record.