Confusion over when A2 can recover throw-in in back court

[udbrky]

I'm watching the rules video sent out this week. Coming back to basketball after 15 years off...

In the Team Control Throw In part, this is confusing me.

A1 throws in, B1 deflects it in the front court, and ball goes into the back court. A2 jumps from front court, Grabs ball lands in back court, back court violation.

A1 throw in, A2 fumbles the throwin in the front court, and it goes into the back court, where he recovers it. Legal.

Why can A2 fumble the throw in in the front court and recover in the back court, but if B1 deflects it, he can't recover in the back court?

The video says they'll most likely review it next season, and the first scenario was discussed a lot. But this does not make much sense.