Of course, using the boot is not as good as gathering the ball & keeping control of it. ...

But, if the goalie is only placing his body on the line (ok, that's not quite what I meant) to block the ball, then a rebound from his head/body/arms/legs has the same effect as getting his foot to it. The main difference is that if he clears it with his boot then he's still on his feet to cope with whatever comes next.

It's a split second choice which can only be made by the goalie.

Also remember that the goalie has to consider where the ball has come from. If it has touched one of his own team on its way back to him, then handling it could cost his team a free kick if the ref construes it as a pass to the goalie. In these circumstances a kick is the only reasonable option. (this rule came after MtheGM's goal-keeping days)

As the original post is just concerned with a single picture then we can't know the circumstances in which this happened.