Is Boult suffering from injury right now??? Or still just struggling to get himself 100% right???
As someone who suffered stress fractures as a young cricketer i know my back was never quite the same and my bowling suffered greatly.
He was clearly still feeling the effects of injury and rehabilitation when playing in Australia at the start of summer.
He's fit now. Or at least bowling at full pace without any obvious signs of grimace or discomfort. He had stress fractures as a youngster before national representation. So they're not new to him.
But his ball release is now stuffed since comming back from injury. The ball is not being released like it used to be. The seam is angled in, possibly too much as an observation, when trying to get the inswinger (though the seam holds its line, the cherry aint swinging), and the seam is wobbly when going for his stock ball outswinger, and not swinging out. (These descriptions are for Left Hand Batsmen facing him).
He used to be textbook. There used to be a lovely counter rotation on the ball as it "floated" down the pitch with the seam holding its given line at between 130 and 140 km per hour and then went in the intended direction. Sometimes before it pitched. Sometimes after. He was dangerous and could carve out the best batsmen in the world.
For now, he is a just a seamer, with limited very seam movement.