How Tamper Proof are the BVG / PSA / SGC cases?

[JMprime]

Hello All,
I am new to this forum. I have started set building some of the 1950's sets and heard this was a great forum, glad to be a part of it.

I recently purchased a 1953 Bowman Card graded by BVG. When I received it, I noticed that there were some slight stress cracks (that is probably the best description) in the plastic on the right hand edge. A few up by the tag, and a few about midway down on that right edge. The two pieces are seated correctly, I compared it to a few BGS cases I had.

I also looked at the history of this particular card on VintageCard, and as far as I can tell, the same card that was sold to me, is in earlier pictures as well.

Sorry to be longwinded. My question is, can a BVG (Or PSA and SGC for that matter) case be opened and cards switched out without breaking the plastic? Is this something commonplace to worry about?

I just wanted to know some of the experienced members opinions. Thanks! Have a great weekend!