Ryan Hall may have spoken to Leon, Hartmann, etc, but they weren't in the lead pack at that point anyway.
I think Leon is off slightly in his narrative. Going by the splits page on the results website, he was 5 to 7 seconds behind Hall from 20k to halfway (65:21 to Leon, 65:14 for Hall). By this time, the chasers were already a good 100-200 meters ahead (for ex, 64:51 for Geneti, 64:52 for Chebet). So if Leon caught Hall sometime between 21k and 25k, when Hall supposedly gave him his advice, he was already too far behind to make any difference! It's not like he was going to suddenly make up 20 or 30 seconds on the guys ahead. By 25k Leon was just falling further behind the lead group (~40 seconds), so was well beyond having the ability to affect them at that point.
The point is, the guys Ryan Hall was talking to were already too far behind to do anything anyway!
So what did Hall actually say? "Don't go catching those guys who are out of contact and pulling away already"?
Verdict: Ryan Hall had no effect on the outcome.