Unless you're talking about a different type of sandboxing to the one that recently went live, discussed in another thread, I don't think it's going to have that effect. It's more stopping visual developers poking around in the core functionality of the product. It doesn't mean that the frameworks that get injected into the sandbox can't still change at a moments notice (or without notice).
The drill issue i'm experiencing felt more like the above - as if how the service responds to the selection manager's events had changed, but given the absence of anyone else seeing the same, i'll have to go see if I can figure this one out alone whether it's this or something else.
A nod from MS on whether anything has changed in this area would be very useful, if anyone is watching this.