Is this contact a blocking foul or player control foul?
This is a difficult play and the answers could be split down the middle. The secondary defender appears to obtain a legal guarding position prior to contact and complies with rule 4-23 articles 1, 2, 3 and 4 and is not moving toward white #10 when the contact occurs.  Though the contact is not in the sternum, it is in the torso of black #11 which is by rule a charging foul. (4-7) Principle to Remember:  If the defender is legal, he/she is not responsible for contact.

Was the Lead official in good position to observe the contact on the play?
While the Lead official was in pretty good position when the play started, as the play developed his angle was reduced and when the contact occurred, he did not have as open a look as he could have if he would have adjusted his position by moving to his right.  The teaching point, even as the Lead we need to adjust our position to have the open angle look found on page 110 of the IAABO manual.

Let’s discuss the Lead’s mechanics and signaling on the play.
As he administers the throw-in, the Lead official properly has a visible 5 second count.  However, he does not show the “time out” signal or signal the timer to start the clock when the throw-in is legally touched. Please review pages 40-43 of the manual.
When the contact occurs the official does not “stop the clock” but immediately signals a blocking foul. By not stopping the clock, the official does not give himself the opportunity to review the play mentally before giving the preliminary signal.  By not stopping the clock first, we also put our crew at risk for aadouble foul when one official signals a player control foul and another official signals a blocking foul.
Finally, when reporting the foul, hustle to the reporting area, stop, establish eye contact with the scorer and report the foul.  See pages 54-58 of the IAABO manual.