Right, I get that, but how much can it take? Using simple numbers for discussion, if the compressor wheel is taking in 5psi and the BOV dumps 10psi in front of it will that additional 5psi be forced through the compressor or go out the air filter? That was my train of thought ...
This got long, but I'll try and show my thoughts on it.
In it's normal state, and especially when chooching, the compressor wheel is in a small vacuum. It is sucking air through a pipe and filter. It's not intake manifold on a gasser at idle levels of vacuum, but less than atmospheric pressure. For simplicity and not switching units to inches of vacuum, we'll say it's seeing approximately 0 psi at the intake side of the compressor wheel. Think of the air filter indicators on most heavy equipment and semis. They show the filter status based on the level of vacuum behind the filter.
While venting via BOV the turbo is still spinning, but slowing down so it is actively pulling air into itself. With a captured BOV, it's pulling that bypassed air from further up the cold side.
Could it go out the filter. In theory yes, but the engine is still consuming some air, and the BOV is only venting the excessive pressure. So it's not necessarily sending a full 10psi down the vent (to atmosphere or back to intake). When engine speed decreases the exhaust drive pressure decreases as well, slowing down the turbine speed from that side as well. Think of ricer movies, that BOV sound is very short, just that quick excess pressure burst when the throttle is quickly closed while the turbo is still full steam ahead.
In the case of using an intake returned BOV to limit total boost, then the engine is still pulling in plenty of air and energy isn't free, so that excessive pressure won't compound in the turbo, just less air will come through the filter. This is why MAF systems prefer to return the BOV to the cold side, as that air is already accounted for. If vented to atmosphere, the engine is not consuming as much air as the MAF has calculated and it'll be rich while the BOV is venting to atmosphere.
Air pressure also will dissipate when going into a larger volume, so 10psi through the relatively small BOV vent into the larger intake tract that was at a slight vacuum will be less than 10psi after entering the larger container.