Achilles injuries are graded in severity and have differing time frames for recovery.
Also, since Berien was fast he has much further to go to regain fitness. They aren't paying him to run 1:47.
Only an idiot would consider a reduction clause motivational. That's just another Nike lie.
Long rehab wrote:
Since August 2016? I ruptured my achilles and was back racing in 8 months.
I imagine when he started up training again this year he strained it again. Then he was faced with the unpleasant decision of continuing to train on it and making it worse or sitting out the year and letting it heal.